mirror of
https://github.com/team-infusion-developers/android_kernel_samsung_msm8976.git
synced 2024-09-21 03:43:03 +00:00
0896f287e4
ARM64 currently doesn't fix up faults on the single-byte (strb) case of
__clear_user... which means that we can cause a nasty kernel panic as an
ordinary user with any multiple PAGE_SIZE+1 read from /dev/zero.
i.e.: dd if=/dev/zero of=foo ibs=1 count=1 (or ibs=65537, etc.)
This is a pretty obscure bug in the general case since we'll only
__do_kernel_fault (since there's no extable entry for pc) if the
mmap_sem is contended. However, with CONFIG_DEBUG_VM enabled, we'll
always fault.
if (!down_read_trylock(&mm->mmap_sem)) {
if (!user_mode(regs) && !search_exception_tables(regs->pc))
goto no_context;
retry:
down_read(&mm->mmap_sem);
} else {
/*
* The above down_read_trylock() might have succeeded in
* which
* case, we'll have missed the might_sleep() from
* down_read().
*/
might_sleep();
if (!user_mode(regs) && !search_exception_tables(regs->pc))
goto no_context;
}
Fix that by adding an extable entry for the strb instruction, since it
touches user memory, similar to the other stores in __clear_user.
Change-Id: I7256cecee5ff3f8f5958d3f7f39ad6b4e761c828
Signed-off-by: Kyle McMartin <kyle@redhat.com>
Reported-by: Miloš Prchlík <mprchlik@redhat.com>
Cc: stable@vger.kernel.org
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Git-commit: 97fc15436b36ee3956efad83e22a557991f7d19d
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
Signed-off-by: Trilok Soni <tsoni@codeaurora.org>
59 lines
1.4 KiB
ArmAsm
59 lines
1.4 KiB
ArmAsm
/*
|
|
* Based on arch/arm/lib/clear_user.S
|
|
*
|
|
* Copyright (C) 2012 ARM Ltd.
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
* published by the Free Software Foundation.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
* GNU General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU General Public License
|
|
* along with this program. If not, see <http://www.gnu.org/licenses/>.
|
|
*/
|
|
#include <linux/linkage.h>
|
|
#include <asm/assembler.h>
|
|
|
|
.text
|
|
|
|
/* Prototype: int __clear_user(void *addr, size_t sz)
|
|
* Purpose : clear some user memory
|
|
* Params : addr - user memory address to clear
|
|
* : sz - number of bytes to clear
|
|
* Returns : number of bytes NOT cleared
|
|
*
|
|
* Alignment fixed up by hardware.
|
|
*/
|
|
ENTRY(__clear_user)
|
|
mov x2, x1 // save the size for fixup return
|
|
subs x1, x1, #8
|
|
b.mi 2f
|
|
1:
|
|
USER(9f, str xzr, [x0], #8 )
|
|
subs x1, x1, #8
|
|
b.pl 1b
|
|
2: adds x1, x1, #4
|
|
b.mi 3f
|
|
USER(9f, str wzr, [x0], #4 )
|
|
sub x1, x1, #4
|
|
3: adds x1, x1, #2
|
|
b.mi 4f
|
|
USER(9f, strh wzr, [x0], #2 )
|
|
sub x1, x1, #2
|
|
4: adds x1, x1, #1
|
|
b.mi 5f
|
|
USER(9f, strb wzr, [x0] )
|
|
5: mov x0, #0
|
|
ret
|
|
ENDPROC(__clear_user)
|
|
|
|
.section .fixup,"ax"
|
|
.align 2
|
|
9: mov x0, x2 // return the original size
|
|
ret
|
|
.previous
|