mtd: spi-nor: aspeed-smc: Use io string accessors to fifo #50
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
mdmillerii
force-pushed
the
aspeed-smc-fifo
branch
from
b676496 to
e5f2fc3
Compare
Make and use new routines to access the fifo when in user mode. Instead of using memcpy_fromio, base the new routines on the io port string accessors. When the smc controllers are configured to transfer in user mode, the exact address within the chip select region is ignored and all valid data bytes are sent to the device fifo. It has been determined the reason _memcpy_fromio, an arm specific byte-by-byte variant of memcpy_fromio was required in read_reg, is that the later will stutter when coping from memory, discarding some bytes read, when switching from words to bytes for the final unaligned length. This change includes a hack to make inw/outw work. The default generic IO_SPACE_LIMIT is 0, and twenty bits when PCI is selected. While there is a PCMCIA SOC config to select the full 4GB space it would bring in the PCMCIA core for no use to the ast2400. We want to be part of the generic multi-platform arm kernel and therefore mach/io.h is not going to work. However, the limit is under an ifndef, so define it in this file an check it was not redefine at probe time. To avoid redefinition errors or warnings, guard the setting with CONFIG_ARM for cross-arch compile testing and with a Kconfig dependency for arm cross-compile tests. While some other architecture may not accept unsigned long addresses as ioport cookies, that can be addressed when, if ever, the hardware appears on another arch. While the change to use the designed-for-memory optimised copy template, even reusing the bytes of memcpy, was a recent change and only for little endian arm, designing and proposing a patch will take some time and there could be debate if the routine needs to work on changing memory. Signed-off-by: Milton Miller <[email protected]>
mdmillerii
force-pushed
the
aspeed-smc-fifo
branch
from
e5f2fc3 to
1707cdf
Compare
|
Thanks, committed as 908a999. |
shenki
pushed a commit
that referenced
this pull request
Aug 9, 2019
[ Upstream commit 3f167e1 ] ipv4_pdp_add() is called in RCU read-side critical section. So GFP_KERNEL should not be used in the function. This patch make ipv4_pdp_add() to use GFP_ATOMIC instead of GFP_KERNEL. Test commands: gtp-link add gtp1 & gtp-tunnel add gtp1 v1 100 200 1.1.1.1 2.2.2.2 Splat looks like: [ 130.618881] ============================= [ 130.626382] WARNING: suspicious RCU usage [ 130.626994] 5.2.0-rc6+ #50 Not tainted [ 130.627622] ----------------------------- [ 130.628223] ./include/linux/rcupdate.h:266 Illegal context switch in RCU read-side critical section! [ 130.629684] [ 130.629684] other info that might help us debug this: [ 130.629684] [ 130.631022] [ 130.631022] rcu_scheduler_active = 2, debug_locks = 1 [ 130.632136] 4 locks held by gtp-tunnel/1025: [ 130.632925] #0: 000000002b93c8b7 (cb_lock){++++}, at: genl_rcv+0x15/0x40 [ 130.634159] #1: 00000000f17bc999 (genl_mutex){+.+.}, at: genl_rcv_msg+0xfb/0x130 [ 130.635487] #2: 00000000c644ed8e (rtnl_mutex){+.+.}, at: gtp_genl_new_pdp+0x18c/0x1150 [gtp] [ 130.636936] #3: 0000000007a1cde7 (rcu_read_lock){....}, at: gtp_genl_new_pdp+0x187/0x1150 [gtp] [ 130.638348] [ 130.638348] stack backtrace: [ 130.639062] CPU: 1 PID: 1025 Comm: gtp-tunnel Not tainted 5.2.0-rc6+ #50 [ 130.641318] Call Trace: [ 130.641707] dump_stack+0x7c/0xbb [ 130.642252] ___might_sleep+0x2c0/0x3b0 [ 130.642862] kmem_cache_alloc_trace+0x1cd/0x2b0 [ 130.643591] gtp_genl_new_pdp+0x6c5/0x1150 [gtp] [ 130.644371] genl_family_rcv_msg+0x63a/0x1030 [ 130.645074] ? mutex_lock_io_nested+0x1090/0x1090 [ 130.645845] ? genl_unregister_family+0x630/0x630 [ 130.646592] ? debug_show_all_locks+0x2d0/0x2d0 [ 130.647293] ? check_flags.part.40+0x440/0x440 [ 130.648099] genl_rcv_msg+0xa3/0x130 [ ... ] Fixes: 459aa66 ("gtp: add initial driver for datapath of GPRS Tunneling Protocol (GTP-U)") Signed-off-by: Taehee Yoo <[email protected]> Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Sasha Levin <[email protected]>
shenki
pushed a commit
that referenced
this pull request
Aug 9, 2019
[ Upstream commit 1788b85 ] gtp_encap_destroy() is called twice. 1. When interface is deleted. 2. When udp socket is destroyed. either gtp->sk0 or gtp->sk1u could be freed by sock_put() in gtp_encap_destroy(). so, when gtp_encap_destroy() is called again, it would uses freed sk pointer. patch makes gtp_encap_destroy() to set either gtp->sk0 or gtp->sk1u to null. in addition, both gtp->sk0 and gtp->sk1u pointer are protected by rtnl_lock. so, rtnl_lock() is added. Test command: gtp-link add gtp1 & killall gtp-link ip link del gtp1 Splat looks like: [ 83.182767] BUG: KASAN: use-after-free in __lock_acquire+0x3a20/0x46a0 [ 83.184128] Read of size 8 at addr ffff8880cc7d5360 by task ip/1008 [ 83.185567] CPU: 1 PID: 1008 Comm: ip Not tainted 5.2.0-rc6+ #50 [ 83.188469] Call Trace: [ ... ] [ 83.200126] lock_acquire+0x141/0x380 [ 83.200575] ? lock_sock_nested+0x3a/0xf0 [ 83.201069] _raw_spin_lock_bh+0x38/0x70 [ 83.201551] ? lock_sock_nested+0x3a/0xf0 [ 83.202044] lock_sock_nested+0x3a/0xf0 [ 83.202520] gtp_encap_destroy+0x18/0xe0 [gtp] [ 83.203065] gtp_encap_disable.isra.14+0x13/0x50 [gtp] [ 83.203687] gtp_dellink+0x56/0x170 [gtp] [ 83.204190] rtnl_delete_link+0xb4/0x100 [ ... ] [ 83.236513] Allocated by task 976: [ 83.236925] save_stack+0x19/0x80 [ 83.237332] __kasan_kmalloc.constprop.3+0xa0/0xd0 [ 83.237894] kmem_cache_alloc+0xd8/0x280 [ 83.238360] sk_prot_alloc.isra.42+0x50/0x200 [ 83.238874] sk_alloc+0x32/0x940 [ 83.239264] inet_create+0x283/0xc20 [ 83.239684] __sock_create+0x2dd/0x540 [ 83.240136] __sys_socket+0xca/0x1a0 [ 83.240550] __x64_sys_socket+0x6f/0xb0 [ 83.240998] do_syscall_64+0x9c/0x450 [ 83.241466] entry_SYSCALL_64_after_hwframe+0x49/0xbe [ 83.242061] [ 83.242249] Freed by task 0: [ 83.242616] save_stack+0x19/0x80 [ 83.243013] __kasan_slab_free+0x111/0x150 [ 83.243498] kmem_cache_free+0x89/0x250 [ 83.244444] __sk_destruct+0x38f/0x5a0 [ 83.245366] rcu_core+0x7e9/0x1c20 [ 83.245766] __do_softirq+0x213/0x8fa Fixes: 1e3a3ab ("gtp: make GTP sockets in gtp_newlink optional") Signed-off-by: Taehee Yoo <[email protected]> Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Sasha Levin <[email protected]>
shenki
pushed a commit
that referenced
this pull request
Aug 9, 2019
[ Upstream commit a2bed90 ] Current gtp_newlink() could be called after unregister_pernet_subsys(). gtp_newlink() uses gtp_net but it can be destroyed by unregister_pernet_subsys(). So unregister_pernet_subsys() should be called after rtnl_link_unregister(). Test commands: #SHELL 1 while : do for i in {1..5} do ./gtp-link add gtp$i & done killall gtp-link done #SHELL 2 while : do modprobe -rv gtp done Splat looks like: [ 753.176631] BUG: KASAN: use-after-free in gtp_newlink+0x9b4/0xa5c [gtp] [ 753.177722] Read of size 8 at addr ffff8880d48f2458 by task gtp-link/7126 [ 753.179082] CPU: 0 PID: 7126 Comm: gtp-link Tainted: G W 5.2.0-rc6+ #50 [ 753.185801] Call Trace: [ 753.186264] dump_stack+0x7c/0xbb [ 753.186863] ? gtp_newlink+0x9b4/0xa5c [gtp] [ 753.187583] print_address_description+0xc7/0x240 [ 753.188382] ? gtp_newlink+0x9b4/0xa5c [gtp] [ 753.189097] ? gtp_newlink+0x9b4/0xa5c [gtp] [ 753.189846] __kasan_report+0x12a/0x16f [ 753.190542] ? gtp_newlink+0x9b4/0xa5c [gtp] [ 753.191298] kasan_report+0xe/0x20 [ 753.191893] gtp_newlink+0x9b4/0xa5c [gtp] [ 753.192580] ? __netlink_ns_capable+0xc3/0xf0 [ 753.193370] __rtnl_newlink+0xb9f/0x11b0 [ ... ] [ 753.241201] Allocated by task 7186: [ 753.241844] save_stack+0x19/0x80 [ 753.242399] __kasan_kmalloc.constprop.3+0xa0/0xd0 [ 753.243192] __kmalloc+0x13e/0x300 [ 753.243764] ops_init+0xd6/0x350 [ 753.244314] register_pernet_operations+0x249/0x6f0 [ ... ] [ 753.251770] Freed by task 7178: [ 753.252288] save_stack+0x19/0x80 [ 753.252833] __kasan_slab_free+0x111/0x150 [ 753.253962] kfree+0xc7/0x280 [ 753.254509] ops_free_list.part.11+0x1c4/0x2d0 [ 753.255241] unregister_pernet_operations+0x262/0x390 [ ... ] [ 753.285883] list_add corruption. next->prev should be prev (ffff8880d48f2458), but was ffff8880d497d878. (next. [ 753.287241] ------------[ cut here ]------------ [ 753.287794] kernel BUG at lib/list_debug.c:25! [ 753.288364] invalid opcode: 0000 [#1] SMP DEBUG_PAGEALLOC KASAN PTI [ 753.289099] CPU: 0 PID: 7126 Comm: gtp-link Tainted: G B W 5.2.0-rc6+ #50 [ 753.291036] RIP: 0010:__list_add_valid+0x74/0xd0 [ 753.291589] Code: 48 39 da 75 27 48 39 f5 74 36 48 39 dd 74 31 48 83 c4 08 b8 01 00 00 00 5b 5d c3 48 89 d9 48b [ 753.293779] RSP: 0018:ffff8880cae8f398 EFLAGS: 00010286 [ 753.294401] RAX: 0000000000000075 RBX: ffff8880d497d878 RCX: 0000000000000000 [ 753.296260] RDX: 0000000000000075 RSI: 0000000000000008 RDI: ffffed10195d1e69 [ 753.297070] RBP: ffff8880cd250ae0 R08: ffffed101b4bff21 R09: ffffed101b4bff21 [ 753.297899] R10: 0000000000000001 R11: ffffed101b4bff20 R12: ffff8880d497d878 [ 753.298703] R13: 0000000000000000 R14: ffff8880cd250ae0 R15: ffff8880d48f2458 [ 753.299564] FS: 00007f5f79805740(0000) GS:ffff8880da400000(0000) knlGS:0000000000000000 [ 753.300533] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 753.301231] CR2: 00007fe8c7ef4f10 CR3: 00000000b71a6006 CR4: 00000000000606f0 [ 753.302183] Call Trace: [ 753.302530] gtp_newlink+0x5f6/0xa5c [gtp] [ 753.303037] ? __netlink_ns_capable+0xc3/0xf0 [ 753.303576] __rtnl_newlink+0xb9f/0x11b0 [ 753.304092] ? rtnl_link_unregister+0x230/0x230 Fixes: 459aa66 ("gtp: add initial driver for datapath of GPRS Tunneling Protocol (GTP-U)") Signed-off-by: Taehee Yoo <[email protected]> Signed-off-by: David S. Miller <[email protected]> Signed-off-by: Sasha Levin <[email protected]>
shenki
pushed a commit
that referenced
this pull request
May 24, 2021
[ Upstream commit 5bbf219 ] An out of bounds write happens when setting the default power state. KASAN sees this as: [drm] radeon: 512M of GTT memory ready. [drm] GART: num cpu pages 131072, num gpu pages 131072 ================================================================== BUG: KASAN: slab-out-of-bounds in radeon_atombios_parse_power_table_1_3+0x1837/0x1998 [radeon] Write of size 4 at addr ffff88810178d858 by task systemd-udevd/157 CPU: 0 PID: 157 Comm: systemd-udevd Not tainted 5.12.0-E620 #50 Hardware name: eMachines eMachines E620 /Nile , BIOS V1.03 09/30/2008 Call Trace: dump_stack+0xa5/0xe6 print_address_description.constprop.0+0x18/0x239 kasan_report+0x170/0x1a8 radeon_atombios_parse_power_table_1_3+0x1837/0x1998 [radeon] radeon_atombios_get_power_modes+0x144/0x1888 [radeon] radeon_pm_init+0x1019/0x1904 [radeon] rs690_init+0x76e/0x84a [radeon] radeon_device_init+0x1c1a/0x21e5 [radeon] radeon_driver_load_kms+0xf5/0x30b [radeon] drm_dev_register+0x255/0x4a0 [drm] radeon_pci_probe+0x246/0x2f6 [radeon] pci_device_probe+0x1aa/0x294 really_probe+0x30e/0x850 driver_probe_device+0xe6/0x135 device_driver_attach+0xc1/0xf8 __driver_attach+0x13f/0x146 bus_for_each_dev+0xfa/0x146 bus_add_driver+0x2b3/0x447 driver_register+0x242/0x2c1 do_one_initcall+0x149/0x2fd do_init_module+0x1ae/0x573 load_module+0x4dee/0x5cca __do_sys_finit_module+0xf1/0x140 do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xae Without KASAN, this will manifest later when the kernel attempts to allocate memory that was stomped, since it collides with the inline slab freelist pointer: invalid opcode: 0000 [#1] SMP NOPTI CPU: 0 PID: 781 Comm: openrc-run.sh Tainted: G W 5.10.12-gentoo-E620 #2 Hardware name: eMachines eMachines E620 /Nile , BIOS V1.03 09/30/2008 RIP: 0010:kfree+0x115/0x230 Code: 89 c5 e8 75 ea ff ff 48 8b 00 0f ba e0 09 72 63 e8 1f f4 ff ff 41 89 c4 48 8b 45 00 0f ba e0 10 72 0a 48 8b 45 08 a8 01 75 02 <0f> 0b 44 89 e1 48 c7 c2 00 f0 ff ff be 06 00 00 00 48 d3 e2 48 c7 RSP: 0018:ffffb42f40267e10 EFLAGS: 00010246 RAX: ffffd61280ee8d88 RBX: 0000000000000004 RCX: 000000008010000d RDX: 4000000000000000 RSI: ffffffffba1360b0 RDI: ffffd61280ee8d80 RBP: ffffd61280ee8d80 R08: ffffffffb91bebdf R09: 0000000000000000 R10: ffff8fe2c1047ac8 R11: 0000000000000000 R12: 0000000000000000 R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000100 FS: 00007fe80eff6b68(0000) GS:ffff8fe339c00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00007fe80eec7bc0 CR3: 0000000038012000 CR4: 00000000000006f0 Call Trace: __free_fdtable+0x16/0x1f put_files_struct+0x81/0x9b do_exit+0x433/0x94d do_group_exit+0xa6/0xa6 __x64_sys_exit_group+0xf/0xf do_syscall_64+0x33/0x40 entry_SYSCALL_64_after_hwframe+0x44/0xa9 RIP: 0033:0x7fe80ef64bea Code: Unable to access opcode bytes at RIP 0x7fe80ef64bc0. RSP: 002b:00007ffdb1c47528 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7 RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00007fe80ef64bea RDX: 00007fe80ef64f60 RSI: 0000000000000000 RDI: 0000000000000000 RBP: 0000000000000000 R08: 0000000000000001 R09: 0000000000000000 R10: 00007fe80ee2c620 R11: 0000000000000246 R12: 00007fe80eff41e0 R13: 00000000ffffffff R14: 0000000000000024 R15: 00007fe80edf9cd0 Modules linked in: radeon(+) ath5k(+) snd_hda_codec_realtek ... Use a valid power_state index when initializing the "flags" and "misc" and "misc2" fields. Bug: https://bugzilla.kernel.org/show_bug.cgi?id=211537 Reported-by: Erhard F. <[email protected]> Fixes: a48b9b4 ("drm/radeon/kms/pm: add asic specific callbacks for getting power state (v2)") Fixes: 79daedc ("drm/radeon/kms: minor pm cleanups") Signed-off-by: Kees Cook <[email protected]> Signed-off-by: Alex Deucher <[email protected]> Signed-off-by: Sasha Levin <[email protected]>
shenki
pushed a commit
that referenced
this pull request
May 24, 2021
[ Upstream commit d5027ca ] Ritesh reported a bug [1] against UML, noting that it crashed on startup. The backtrace shows the following (heavily redacted): (gdb) bt ... #26 0x0000000060015b5d in sem_init () at ipc/sem.c:268 #27 0x00007f89906d92f7 in ?? () from /lib/x86_64-linux-gnu/libcom_err.so.2 #28 0x00007f8990ab8fb2 in call_init (...) at dl-init.c:72 ... #40 0x00007f89909bf3a6 in nss_load_library (...) at nsswitch.c:359 ... #44 0x00007f8990895e35 in _nss_compat_getgrnam_r (...) at nss_compat/compat-grp.c:486 #45 0x00007f8990968b85 in __getgrnam_r [...] #46 0x00007f89909d6b77 in grantpt [...] #47 0x00007f8990a9394e in __GI_openpty [...] #48 0x00000000604a1f65 in openpty_cb (...) at arch/um/os-Linux/sigio.c:407 #49 0x00000000604a58d0 in start_idle_thread (...) at arch/um/os-Linux/skas/process.c:598 #50 0x0000000060004a3d in start_uml () at arch/um/kernel/skas/process.c:45 #51 0x00000000600047b2 in linux_main (...) at arch/um/kernel/um_arch.c:334 #52 0x000000006000574f in main (...) at arch/um/os-Linux/main.c:144 indicating that the UML function openpty_cb() calls openpty(), which internally calls __getgrnam_r(), which causes the nsswitch machinery to get started. This loads, through lots of indirection that I snipped, the libcom_err.so.2 library, which (in an unknown function, "??") calls sem_init(). Now, of course it wants to get libpthread's sem_init(), since it's linked against libpthread. However, the dynamic linker looks up that symbol against the binary first, and gets the kernel's sem_init(). Hajime Tazaki noted that "objcopy -L" can localize a symbol, so the dynamic linker wouldn't do the lookup this way. I tried, but for some reason that didn't seem to work. Doing the same thing in the linker script instead does seem to work, though I cannot entirely explain - it *also* works if I just add "VERSION { { global: *; }; }" instead, indicating that something else is happening that I don't really understand. It may be that explicitly doing that marks them with some kind of empty version, and that's different from the default. Explicitly marking them with a version breaks kallsyms, so that doesn't seem to be possible. Marking all the symbols as local seems correct, and does seem to address the issue, so do that. Also do it for static link, nsswitch libraries could still be loaded there. [1] https://bugs.debian.org/983379 Reported-by: Ritesh Raj Sarraf <[email protected]> Signed-off-by: Johannes Berg <[email protected]> Acked-By: Anton Ivanov <[email protected]> Tested-By: Ritesh Raj Sarraf <[email protected]> Signed-off-by: Richard Weinberger <[email protected]> Signed-off-by: Sasha Levin <[email protected]>
shenki
pushed a commit
that referenced
this pull request
Apr 14, 2022
commit 6c8e2a2 upstream. Problem: ======= Userspace might read the zero-page instead of actual data from a direct IO read on a block device if the buffers have been called madvise(MADV_FREE) on earlier (this is discussed below) due to a race between page reclaim on MADV_FREE and blkdev direct IO read. - Race condition: ============== During page reclaim, the MADV_FREE page check in try_to_unmap_one() checks if the page is not dirty, then discards its rmap PTE(s) (vs. remap back if the page is dirty). However, after try_to_unmap_one() returns to shrink_page_list(), it might keep the page _anyway_ if page_ref_freeze() fails (it expects exactly _one_ page reference, from the isolation for page reclaim). Well, blkdev_direct_IO() gets references for all pages, and on READ operations it only sets them dirty _later_. So, if MADV_FREE'd pages (i.e., not dirty) are used as buffers for direct IO read from block devices, and page reclaim happens during __blkdev_direct_IO[_simple]() exactly AFTER bio_iov_iter_get_pages() returns, but BEFORE the pages are set dirty, the situation happens. The direct IO read eventually completes. Now, when userspace reads the buffers, the PTE is no longer there and the page fault handler do_anonymous_page() services that with the zero-page, NOT the data! A synthetic reproducer is provided. - Page faults: =========== If page reclaim happens BEFORE bio_iov_iter_get_pages() the issue doesn't happen, because that faults-in all pages as writeable, so do_anonymous_page() sets up a new page/rmap/PTE, and that is used by direct IO. The userspace reads don't fault as the PTE is there (thus zero-page is not used/setup). But if page reclaim happens AFTER it / BEFORE setting pages dirty, the PTE is no longer there; the subsequent page faults can't help: The data-read from the block device probably won't generate faults due to DMA (no MMU) but even in the case it wouldn't use DMA, that happens on different virtual addresses (not user-mapped addresses) because `struct bio_vec` stores `struct page` to figure addresses out (which are different from user-mapped addresses) for the read. Thus userspace reads (to user-mapped addresses) still fault, then do_anonymous_page() gets another `struct page` that would address/ map to other memory than the `struct page` used by `struct bio_vec` for the read. (The original `struct page` is not available, since it wasn't freed, as page_ref_freeze() failed due to more page refs. And even if it were available, its data cannot be trusted anymore.) Solution: ======== One solution is to check for the expected page reference count in try_to_unmap_one(). There should be one reference from the isolation (that is also checked in shrink_page_list() with page_ref_freeze()) plus one or more references from page mapping(s) (put in discard: label). Further references mean that rmap/PTE cannot be unmapped/nuked. (Note: there might be more than one reference from mapping due to fork()/clone() without CLONE_VM, which use the same `struct page` for references, until the copy-on-write page gets copied.) So, additional page references (e.g., from direct IO read) now prevent the rmap/PTE from being unmapped/dropped; similarly to the page is not freed per shrink_page_list()/page_ref_freeze()). - Races and Barriers: ================== The new check in try_to_unmap_one() should be safe in races with bio_iov_iter_get_pages() in get_user_pages() fast and slow paths, as it's done under the PTE lock. The fast path doesn't take the lock, but it checks if the PTE has changed and if so, it drops the reference and leaves the page for the slow path (which does take that lock). The fast path requires synchronization w/ full memory barrier: it writes the page reference count first then it reads the PTE later, while try_to_unmap() writes PTE first then it reads page refcount. And a second barrier is needed, as the page dirty flag should not be read before the page reference count (as in __remove_mapping()). (This can be a load memory barrier only; no writes are involved.) Call stack/comments: - try_to_unmap_one() - page_vma_mapped_walk() - map_pte() # see pte_offset_map_lock(): pte_offset_map() spin_lock() - ptep_get_and_clear() # write PTE - smp_mb() # (new barrier) GUP fast path - page_ref_count() # (new check) read refcount - page_vma_mapped_walk_done() # see pte_unmap_unlock(): pte_unmap() spin_unlock() - bio_iov_iter_get_pages() - __bio_iov_iter_get_pages() - iov_iter_get_pages() - get_user_pages_fast() - internal_get_user_pages_fast() # fast path - lockless_pages_from_mm() - gup_{pgd,p4d,pud,pmd,pte}_range() ptep = pte_offset_map() # not _lock() pte = ptep_get_lockless(ptep) page = pte_page(pte) try_grab_compound_head(page) # inc refcount # (RMW/barrier # on success) if (pte_val(pte) != pte_val(*ptep)) # read PTE put_compound_head(page) # dec refcount # go slow path # slow path - __gup_longterm_unlocked() - get_user_pages_unlocked() - __get_user_pages_locked() - __get_user_pages() - follow_{page,p4d,pud,pmd}_mask() - follow_page_pte() ptep = pte_offset_map_lock() pte = *ptep page = vm_normal_page(pte) try_grab_page(page) # inc refcount pte_unmap_unlock() - Huge Pages: ========== Regarding transparent hugepages, that logic shouldn't change, as MADV_FREE (aka lazyfree) pages are PageAnon() && !PageSwapBacked() (madvise_free_pte_range() -> mark_page_lazyfree() -> lru_lazyfree_fn()) thus should reach shrink_page_list() -> split_huge_page_to_list() before try_to_unmap[_one](), so it deals with normal pages only. (And in case unlikely/TTU_SPLIT_HUGE_PMD/split_huge_pmd_address() happens, which should not or be rare, the page refcount should be greater than mapcount: the head page is referenced by tail pages. That also prevents checking the head `page` then incorrectly call page_remove_rmap(subpage) for a tail page, that isn't even in the shrink_page_list()'s page_list (an effect of split huge pmd/pmvw), as it might happen today in this unlikely scenario.) MADV_FREE'd buffers: =================== So, back to the "if MADV_FREE pages are used as buffers" note. The case is arguable, and subject to multiple interpretations. The madvise(2) manual page on the MADV_FREE advice value says: 1) 'After a successful MADV_FREE ... data will be lost when the kernel frees the pages.' 2) 'the free operation will be canceled if the caller writes into the page' / 'subsequent writes ... will succeed and then [the] kernel cannot free those dirtied pages' 3) 'If there is no subsequent write, the kernel can free the pages at any time.' Thoughts, questions, considerations... respectively: 1) Since the kernel didn't actually free the page (page_ref_freeze() failed), should the data not have been lost? (on userspace read.) 2) Should writes performed by the direct IO read be able to cancel the free operation? - Should the direct IO read be considered as 'the caller' too, as it's been requested by 'the caller'? - Should the bio technique to dirty pages on return to userspace (bio_check_pages_dirty() is called/used by __blkdev_direct_IO()) be considered in another/special way here? 3) Should an upcoming write from a previously requested direct IO read be considered as a subsequent write, so the kernel should not free the pages? (as it's known at the time of page reclaim.) And lastly: Technically, the last point would seem a reasonable consideration and balance, as the madvise(2) manual page apparently (and fairly) seem to assume that 'writes' are memory access from the userspace process (not explicitly considering writes from the kernel or its corner cases; again, fairly).. plus the kernel fix implementation for the corner case of the largely 'non-atomic write' encompassed by a direct IO read operation, is relatively simple; and it helps. Reproducer: ========== @ test.c (simplified, but works) #define _GNU_SOURCE #include <fcntl.h> #include <stdio.h> #include <unistd.h> #include <sys/mman.h> int main() { int fd, i; char *buf; fd = open(DEV, O_RDONLY | O_DIRECT); buf = mmap(NULL, BUF_SIZE, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0); for (i = 0; i < BUF_SIZE; i += PAGE_SIZE) buf[i] = 1; // init to non-zero madvise(buf, BUF_SIZE, MADV_FREE); read(fd, buf, BUF_SIZE); for (i = 0; i < BUF_SIZE; i += PAGE_SIZE) printf("%p: 0x%x\n", &buf[i], buf[i]); return 0; } @ block/fops.c (formerly fs/block_dev.c) +#include <linux/swap.h> ... ... __blkdev_direct_IO[_simple](...) { ... + if (!strcmp(current->comm, "good")) + shrink_all_memory(ULONG_MAX); + ret = bio_iov_iter_get_pages(...); + + if (!strcmp(current->comm, "bad")) + shrink_all_memory(ULONG_MAX); ... } @ shell # NUM_PAGES=4 # PAGE_SIZE=$(getconf PAGE_SIZE) # yes | dd of=test.img bs=${PAGE_SIZE} count=${NUM_PAGES} # DEV=$(losetup -f --show test.img) # gcc -DDEV=\"$DEV\" \ -DBUF_SIZE=$((PAGE_SIZE * NUM_PAGES)) \ -DPAGE_SIZE=${PAGE_SIZE} \ test.c -o test # od -tx1 $DEV 0000000 79 0a 79 0a 79 0a 79 0a 79 0a 79 0a 79 0a 79 0a * 0040000 # mv test good # ./good 0x7f7c10418000: 0x79 0x7f7c10419000: 0x79 0x7f7c1041a000: 0x79 0x7f7c1041b000: 0x79 # mv good bad # ./bad 0x7fa1b8050000: 0x0 0x7fa1b8051000: 0x0 0x7fa1b8052000: 0x0 0x7fa1b8053000: 0x0 Note: the issue is consistent on v5.17-rc3, but it's intermittent with the support of MADV_FREE on v4.5 (60%-70% error; needs swap). [wrap do_direct_IO() in do_blockdev_direct_IO() @ fs/direct-io.c]. - v5.17-rc3: # for i in {1..1000}; do ./good; done \ | cut -d: -f2 | sort | uniq -c 4000 0x79 # mv good bad # for i in {1..1000}; do ./bad; done \ | cut -d: -f2 | sort | uniq -c 4000 0x0 # free | grep Swap Swap: 0 0 0 - v4.5: # for i in {1..1000}; do ./good; done \ | cut -d: -f2 | sort | uniq -c 4000 0x79 # mv good bad # for i in {1..1000}; do ./bad; done \ | cut -d: -f2 | sort | uniq -c 2702 0x0 1298 0x79 # swapoff -av swapoff /swap # for i in {1..1000}; do ./bad; done \ | cut -d: -f2 | sort | uniq -c 4000 0x79 Ceph/TCMalloc: ============= For documentation purposes, the use case driving the analysis/fix is Ceph on Ubuntu 18.04, as the TCMalloc library there still uses MADV_FREE to release unused memory to the system from the mmap'ed page heap (might be committed back/used again; it's not munmap'ed.) - PageHeap::DecommitSpan() -> TCMalloc_SystemRelease() -> madvise() - PageHeap::CommitSpan() -> TCMalloc_SystemCommit() -> do nothing. Note: TCMalloc switched back to MADV_DONTNEED a few commits after the release in Ubuntu 18.04 (google-perftools/gperftools 2.5), so the issue just 'disappeared' on Ceph on later Ubuntu releases but is still present in the kernel, and can be hit by other use cases. The observed issue seems to be the old Ceph bug #22464 [1], where checksum mismatches are observed (and instrumentation with buffer dumps shows zero-pages read from mmap'ed/MADV_FREE'd page ranges). The issue in Ceph was reasonably deemed a kernel bug (comment #50) and mostly worked around with a retry mechanism, but other parts of Ceph could still hit that (rocksdb). Anyway, it's less likely to be hit again as TCMalloc switched out of MADV_FREE by default. (Some kernel versions/reports from the Ceph bug, and relation with the MADV_FREE introduction/changes; TCMalloc versions not checked.) - 4.4 good - 4.5 (madv_free: introduction) - 4.9 bad - 4.10 good? maybe a swapless system - 4.12 (madv_free: no longer free instantly on swapless systems) - 4.13 bad [1] https://tracker.ceph.com/issues/22464 Thanks: ====== Several people contributed to analysis/discussions/tests/reproducers in the first stages when drilling down on ceph/tcmalloc/linux kernel: - Dan Hill - Dan Streetman - Dongdong Tao - Gavin Guo - Gerald Yang - Heitor Alves de Siqueira - Ioanna Alifieraki - Jay Vosburgh - Matthew Ruffell - Ponnuvel Palaniyappan Reviews, suggestions, corrections, comments: - Minchan Kim - Yu Zhao - Huang, Ying - John Hubbard - Christoph Hellwig [[email protected]: v4] Link: https://lkml.kernel.org/r/[email protected]: https://lkml.kernel.org/r/[email protected] Fixes: 802a3a9 ("mm: reclaim MADV_FREE pages") Signed-off-by: Mauricio Faria de Oliveira <[email protected]> Reviewed-by: "Huang, Ying" <[email protected]> Cc: Minchan Kim <[email protected]> Cc: Yu Zhao <[email protected]> Cc: Yang Shi <[email protected]> Cc: Miaohe Lin <[email protected]> Cc: Dan Hill <[email protected]> Cc: Dan Streetman <[email protected]> Cc: Dongdong Tao <[email protected]> Cc: Gavin Guo <[email protected]> Cc: Gerald Yang <[email protected]> Cc: Heitor Alves de Siqueira <[email protected]> Cc: Ioanna Alifieraki <[email protected]> Cc: Jay Vosburgh <[email protected]> Cc: Matthew Ruffell <[email protected]> Cc: Ponnuvel Palaniyappan <[email protected]> Cc: <[email protected]> Cc: Christoph Hellwig <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]> [mfo: backport: replace folio/test_flag with page/flag equivalents; real Fixes: 854e9ed ("mm: support madvise(MADV_FREE)") in v4.] Signed-off-by: Mauricio Faria de Oliveira <[email protected]> Signed-off-by: Sasha Levin <[email protected]>
shenki
pushed a commit
that referenced
this pull request
Oct 26, 2023
[ Upstream commit 9989214 ] Commit a1d7671 ("md: use mddev->external to select holder in export_rdev()") fix the problem that 'claim_rdev' is used for blkdev_get_by_dev() while 'rdev' is used for blkdev_put(). However, if mddev->external is changed from 0 to 1, then 'rdev' is used for blkdev_get_by_dev() while 'claim_rdev' is used for blkdev_put(). And this problem can be reporduced reliably by following: New file: mdadm/tests/23rdev-lifetime devname=${dev0##*/} devt=`cat /sys/block/$devname/dev` pid="" runtime=2 clean_up_test() { pill -9 $pid echo clear > /sys/block/md0/md/array_state } trap 'clean_up_test' EXIT add_by_sysfs() { while true; do echo $devt > /sys/block/md0/md/new_dev done } remove_by_sysfs(){ while true; do echo remove > /sys/block/md0/md/dev-${devname}/state done } echo md0 > /sys/module/md_mod/parameters/new_array || die "create md0 failed" add_by_sysfs & pid="$pid $!" remove_by_sysfs & pid="$pid $!" sleep $runtime exit 0 Test cmd: ./test --save-logs --logdir=/tmp/ --keep-going --dev=loop --tests=23rdev-lifetime Test result: ------------[ cut here ]------------ WARNING: CPU: 0 PID: 960 at block/bdev.c:618 blkdev_put+0x27c/0x330 Modules linked in: multipath md_mod loop CPU: 0 PID: 960 Comm: test Not tainted 6.5.0-rc2-00121-g01e55c376936-dirty #50 RIP: 0010:blkdev_put+0x27c/0x330 Call Trace: <TASK> export_rdev.isra.23+0x50/0xa0 [md_mod] mddev_unlock+0x19d/0x300 [md_mod] rdev_attr_store+0xec/0x190 [md_mod] sysfs_kf_write+0x52/0x70 kernfs_fop_write_iter+0x19a/0x2a0 vfs_write+0x3b5/0x770 ksys_write+0x74/0x150 __x64_sys_write+0x22/0x30 do_syscall_64+0x40/0x90 entry_SYSCALL_64_after_hwframe+0x63/0xcd Fix the problem by recording if 'rdev' is used as holder. Fixes: a1d7671 ("md: use mddev->external to select holder in export_rdev()") Signed-off-by: Yu Kuai <[email protected]> Signed-off-by: Song Liu <[email protected]> Link: https://lore.kernel.org/r/[email protected] Signed-off-by: Sasha Levin <[email protected]>
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Here is the patch that allows jffs2 to mount.
Please review.