console: consume APC, DM, DCS

jira LE-1907
cve CVE-2021-3753
Rebuild_History Non-Buildable kernel-4.18.0-524.el8
commit-author nick black <[email protected]>
commit 3a2b2eb
Empty-Commit: Cherry-Pick Conflicts during history rebuild.
Will be included in final tarball splat. Ref for failed cherry-pick at:
ciq/ciq_backports/kernel-4.18.0-524.el8/3a2b2eb5.failed

The Linux console's VT102 implementation already consumes OSC
("Operating System Command") sequences, probably because that's how
palette changes are transmitted.

In addition to OSC, there are three other major clases of ANSI control
strings: APC ("Application Program Command"), PM ("Privacy Message"),
and DCS ("Device Control String").  They are handled similarly to OSC in
terms of termination.

Source: vt100.net

Add three new enumerated states, one for each of these types.  All three
are handled the same way right now--they simply consume input until
terminated.  I hope to expand upon this firmament in the future.  Add
new predicate ansi_control_string(), returning true for any of these
states.  Replace explicit checks against ESosc with calls to this
function.  Transition to these states appropriately from the escape
initiation (ESesc) state.

This was motivated by the following Notcurses bugs:

 dankamongmen/notcurses#2050
 dankamongmen/notcurses#1828
 dankamongmen/notcurses#2069

where standard VT sequences are not consumed by the Linux console.  It's
not necessary that the Linux console *support* these sequences, but it
ought *consume* these well-specified classes of sequences.

Tested by sending a variety of escape sequences to the console, and
verifying that they still worked, or were now properly consumed.
Verified that the escapes were properly terminated at a generic level.
Verified that the Notcurses tools continued to show expected output on
the Linux console, except now without escape bleedthrough.

Link: https://lore.kernel.org/lkml/[email protected]/
	Signed-off-by: nick black <[email protected]>
	Cc: Greg Kroah-Hartman <[email protected]>
	Cc: Jiri Slaby <[email protected]>
	Cc: Tetsuo Handa <[email protected]>
	Cc: Daniel Vetter <[email protected]>
	Signed-off-by: Linus Torvalds <[email protected]>
(cherry picked from commit 3a2b2eb)
	Signed-off-by: Jonathan Maple <[email protected]>

# Conflicts:
#	drivers/tty/vt/vt.c

ciq/ciq_backports/kernel-4.18.0-524.el8/3a2b2eb5.failed

@@ -0,0 +1,160 @@
+console: consume APC, DM, DCS
+
+jira LE-1907
+cve CVE-2021-3753
+Rebuild_History Non-Buildable kernel-4.18.0-524.el8
+commit-author nick black <[email protected]>
+commit 3a2b2eb55681158d3e3ef464fbf47574cf0c517c
+Empty-Commit: Cherry-Pick Conflicts during history rebuild.
+Will be included in final tarball splat. Ref for failed cherry-pick at:
+ciq/ciq_backports/kernel-4.18.0-524.el8/3a2b2eb5.failed
+
+The Linux console's VT102 implementation already consumes OSC
+("Operating System Command") sequences, probably because that's how
+palette changes are transmitted.
+
+In addition to OSC, there are three other major clases of ANSI control
+strings: APC ("Application Program Command"), PM ("Privacy Message"),
+and DCS ("Device Control String").  They are handled similarly to OSC in
+terms of termination.
+
+Source: vt100.net
+
+Add three new enumerated states, one for each of these types.  All three
+are handled the same way right now--they simply consume input until
+terminated.  I hope to expand upon this firmament in the future.  Add
+new predicate ansi_control_string(), returning true for any of these
+states.  Replace explicit checks against ESosc with calls to this
+function.  Transition to these states appropriately from the escape
+initiation (ESesc) state.
+
+This was motivated by the following Notcurses bugs:
+
+ https://github.com/dankamongmen/notcurses/issues/2050
+ https://github.com/dankamongmen/notcurses/issues/1828
+ https://github.com/dankamongmen/notcurses/issues/2069
+
+where standard VT sequences are not consumed by the Linux console.  It's
+not necessary that the Linux console *support* these sequences, but it
+ought *consume* these well-specified classes of sequences.
+
+Tested by sending a variety of escape sequences to the console, and
+verifying that they still worked, or were now properly consumed.
+Verified that the escapes were properly terminated at a generic level.
+Verified that the Notcurses tools continued to show expected output on
+the Linux console, except now without escape bleedthrough.
+
+Link: https://lore.kernel.org/lkml/[email protected]/
+	Signed-off-by: nick black <[email protected]>
+	Cc: Greg Kroah-Hartman <[email protected]>
+	Cc: Jiri Slaby <[email protected]>
+	Cc: Tetsuo Handa <[email protected]>
+	Cc: Daniel Vetter <[email protected]>
+	Signed-off-by: Linus Torvalds <[email protected]>
+(cherry picked from commit 3a2b2eb55681158d3e3ef464fbf47574cf0c517c)
+	Signed-off-by: Jonathan Maple <[email protected]>
+
+# Conflicts:
+#	drivers/tty/vt/vt.c
+diff --cc drivers/tty/vt/vt.c
+index a1e786760faa,cb72393f92d3..000000000000
+--- a/drivers/tty/vt/vt.c
++++ b/drivers/tty/vt/vt.c
+@@@ -1908,8 -2058,8 +1908,13 @@@ static void restore_cur(struct vc_data 
+  }
+
+  enum { ESnormal, ESesc, ESsquare, ESgetpars, ESfunckey,
+++<<<<<<< HEAD
+ +	EShash, ESsetG0, ESsetG1, ESpercent, ESignore, ESnonstd,
+ +	ESpalette, ESosc };
+++=======
++ 	EShash, ESsetG0, ESsetG1, ESpercent, EScsiignore, ESnonstd,
++ 	ESpalette, ESosc, ESapc, ESpm, ESdcs };
+++>>>>>>> 3a2b2eb55681 (console: consume APC, DM, DCS)
+
+  /* console_lock is held (except via vc_init()) */
+  static void reset_terminal(struct vc_data *vc, int do_clear)
+@@@ -1963,6 -2110,37 +1968,40 @@@
+  	    csi_J(vc, 2);
+  }
+
+++<<<<<<< HEAD
+++=======
++ static void vc_setGx(struct vc_data *vc, unsigned int which, int c)
++ {
++ 	unsigned char *charset = &vc->state.Gx_charset[which];
++ 
++ 	switch (c) {
++ 	case '0':
++ 		*charset = GRAF_MAP;
++ 		break;
++ 	case 'B':
++ 		*charset = LAT1_MAP;
++ 		break;
++ 	case 'U':
++ 		*charset = IBMPC_MAP;
++ 		break;
++ 	case 'K':
++ 		*charset = USER_MAP;
++ 		break;
++ 	}
++ 
++ 	if (vc->state.charset == which)
++ 		vc->vc_translate = set_translate(*charset, vc);
++ }
++ 
++ /* is this state an ANSI control string? */
++ static bool ansi_control_string(unsigned int state)
++ {
++ 	if (state == ESosc || state == ESapc || state == ESpm || state == ESdcs)
++ 		return true;
++ 	return false;
++ }
++ 
+++>>>>>>> 3a2b2eb55681 (console: consume APC, DM, DCS)
+  /* console_lock is held */
+  static void do_con_trol(struct tty_struct *tty, struct vc_data *vc, int c)
+  {
+@@@ -2048,8 -2235,12 +2093,11 @@@
+  			lf(vc);
+  			return;
+  		case 'H':
+ -			if (vc->state.x < VC_TABSTOPS_COUNT)
+ -				set_bit(vc->state.x, vc->vc_tab_stop);
+ +			vc->vc_tab_stop[7 & (vc->vc_x >> 5)] |= (1 << (vc->vc_x & 31));
+  			return;
++ 		case 'P':
++ 			vc->vc_state = ESdcs;
++ 			return;
+  		case 'Z':
+  			respond_ID(tty);
+  			return;
+@@@ -2333,20 -2534,17 +2381,26 @@@
+  		vc->vc_state = ESnormal;
+  		return;
+  	case ESsetG1:
+ -		vc_setGx(vc, 1, c);
+ +		if (c == '0')
+ +			vc->vc_G1_charset = GRAF_MAP;
+ +		else if (c == 'B')
+ +			vc->vc_G1_charset = LAT1_MAP;
+ +		else if (c == 'U')
+ +			vc->vc_G1_charset = IBMPC_MAP;
+ +		else if (c == 'K')
+ +			vc->vc_G1_charset = USER_MAP;
+ +		if (vc->vc_charset == 1)
+ +			vc->vc_translate = set_translate(vc->vc_G1_charset, vc);
+  		vc->vc_state = ESnormal;
+  		return;
++ 	case ESapc:
++ 		return;
+  	case ESosc:
+  		return;
++ 	case ESpm:
++ 		return;
++ 	case ESdcs:
++ 		return;
+  	default:
+  		vc->vc_state = ESnormal;
+  	}
+* Unmerged path drivers/tty/vt/vt.c