From 6f6647a532e320129d7ea12b1e922d834175e9ad Mon Sep 17 00:00:00 2001
From: Wedson Almeida Filho <wedsonaf@google.com>
Date: Thu, 18 Mar 2021 15:26:06 +0000
Subject: [PATCH] Handle possible allocation failure in `user_ptr`.

---
 rust/kernel/error.rs    | 16 +++++++++-------
 rust/kernel/lib.rs      |  8 +++++++-
 rust/kernel/user_ptr.rs | 10 ++++------
 3 files changed, 20 insertions(+), 14 deletions(-)

diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
index 68117e557e863d..ad084420f46e41 100644
--- a/rust/kernel/error.rs
+++ b/rust/kernel/error.rs
@@ -4,13 +4,9 @@
 //!
 //! C header: [`include/uapi/asm-generic/errno-base.h`](../../../include/uapi/asm-generic/errno-base.h)
 
-use core::num::TryFromIntError;
-use core::str::Utf8Error;
-
-use alloc::alloc::AllocError;
-
-use crate::bindings;
-use crate::c_types;
+use crate::{bindings, c_types};
+use alloc::{alloc::AllocError, collections::TryReserveError};
+use core::{num::TryFromIntError, str::Utf8Error};
 
 /// Generic integer kernel error.
 ///
@@ -72,6 +68,12 @@ impl From<Utf8Error> for Error {
     }
 }
 
+impl From<TryReserveError> for Error {
+    fn from(_: TryReserveError) -> Error {
+        Error::ENOMEM
+    }
+}
+
 /// A [`Result`] with an [`Error`] error type.
 ///
 /// To be used as the return type for functions that may fail.
diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
index 49cd6bbe20dae8..504bb0a2149891 100644
--- a/rust/kernel/lib.rs
+++ b/rust/kernel/lib.rs
@@ -12,7 +12,13 @@
 //! do so first instead of bypassing this crate.
 
 #![no_std]
-#![feature(allocator_api, alloc_error_handler, const_fn, const_mut_refs)]
+#![feature(
+    allocator_api,
+    alloc_error_handler,
+    const_fn,
+    const_mut_refs,
+    try_reserve
+)]
 #![deny(clippy::complexity)]
 #![deny(clippy::correctness)]
 #![deny(clippy::perf)]
diff --git a/rust/kernel/user_ptr.rs b/rust/kernel/user_ptr.rs
index fdab26d2f4bb25..82eaea2d769b86 100644
--- a/rust/kernel/user_ptr.rs
+++ b/rust/kernel/user_ptr.rs
@@ -4,12 +4,8 @@
 //!
 //! C header: [`include/linux/uaccess.h`](../../../../include/linux/uaccess.h)
 
-use alloc::vec;
+use crate::{c_types, error};
 use alloc::vec::Vec;
-use core::u32;
-
-use crate::c_types;
-use crate::error;
 
 extern "C" {
     fn rust_helper_access_ok(addr: *const c_types::c_void, len: c_types::c_ulong)
@@ -134,7 +130,9 @@ impl UserSlicePtrReader {
     /// Returns `EFAULT` if the address does not currently point to
     /// mapped, readable memory.
     pub fn read_all(&mut self) -> error::KernelResult<Vec<u8>> {
-        let mut data = vec![0; self.1];
+        let mut data = Vec::<u8>::new();
+        data.try_reserve_exact(self.1)?;
+        data.resize(self.1, 0);
         self.read(&mut data)?;
         Ok(data)
     }