The patch titled
Subject: tmpfs: fix undefined-behaviour in shmem_reconfigure()
has been added to the -mm mm-unstable branch. Its filename is
tmpfs-fix-undefined-behaviour-in-shmem_reconfigure.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/tmpfs-fix-undefined-behaviour-in-shmem_reconfigure.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Luo Meng <luomeng12@xxxxxxxxxx>
Subject: tmpfs: fix undefined-behaviour in shmem_reconfigure()
Date: Fri, 13 May 2022 10:52:25 +0800
When shmem_reconfigure() calls __percpu_counter_compare(), the second
parameter is unsigned long long. But in the definition of
__percpu_counter_compare(), the second parameter is s64. So when
__percpu_counter_compare() executes abs(count - rhs), UBSAN shows the
following warning:
================================================================================
UBSAN: Undefined behaviour in lib/percpu_counter.c:209:6
signed integer overflow:
0 - -9223372036854775808 cannot be represented in type 'long long int'
CPU: 1 PID: 9636 Comm: syz-executor.2 Tainted: G ---------r- - 4.18.0 #2
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.14.0-0-g155821a1990b-prebuilt.qemu.org 04/01/2014
Call Trace:
__dump_stack home/install/linux-rh-3-10/lib/dump_stack.c:77 [inline]
dump_stack+0x125/0x1ae home/install/linux-rh-3-10/lib/dump_stack.c:117
ubsan_epilogue+0xe/0x81 home/install/linux-rh-3-10/lib/ubsan.c:159
handle_overflow+0x19d/0x1ec home/install/linux-rh-3-10/lib/ubsan.c:190
__percpu_counter_compare+0x124/0x140 home/install/linux-rh-3-10/lib/percpu_counter.c:209
percpu_counter_compare home/install/linux-rh-3-10/./include/linux/percpu_counter.h:50 [inline]
shmem_remount_fs+0x1ce/0x6b0 home/install/linux-rh-3-10/mm/shmem.c:3530
do_remount_sb+0x11b/0x530 home/install/linux-rh-3-10/fs/super.c:888
do_remount home/install/linux-rh-3-10/fs/namespace.c:2344 [inline]
do_mount+0xf8d/0x26b0 home/install/linux-rh-3-10/fs/namespace.c:2844
ksys_mount+0xad/0x120 home/install/linux-rh-3-10/fs/namespace.c:3075
__do_sys_mount home/install/linux-rh-3-10/fs/namespace.c:3089 [inline]
__se_sys_mount home/install/linux-rh-3-10/fs/namespace.c:3086 [inline]
__x64_sys_mount+0xbf/0x160 home/install/linux-rh-3-10/fs/namespace.c:3086
do_syscall_64+0xca/0x5c0 home/install/linux-rh-3-10/arch/x86/entry/common.c:298
entry_SYSCALL_64_after_hwframe+0x6a/0xdf
RIP: 0033:0x46b5e9
Code: 5d db fa ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 2b db fa ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f54d5f22c68 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 000000000077bf60 RCX: 000000000046b5e9
RDX: 0000000000000000 RSI: 0000000020000000 RDI: 0000000000000000
RBP: 000000000077bf60 R08: 0000000020000140 R09: 0000000000000000
R10: 00000000026740a4 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd1fb1592f R14: 00007f54d5f239c0 R15: 000000000077bf6c
================================================================================
Link: https://lkml.kernel.org/r/20220513025225.2678727-1-luomeng12@xxxxxxxxxx
Signed-off-by: Luo Meng <luomeng12@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Yu Kuai <yukuai3@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 4 ++++
1 file changed, 4 insertions(+)
--- a/mm/shmem.c~tmpfs-fix-undefined-behaviour-in-shmem_reconfigure
+++ a/mm/shmem.c
@@ -3476,6 +3476,10 @@ static int shmem_reconfigure(struct fs_c
raw_spin_lock(&sbinfo->stat_lock);
inodes = sbinfo->max_inodes - sbinfo->free_inodes;
+ if (ctx->blocks > S64_MAX) {
+ err = "The number of blocks too large";
+ goto out;
+ }
if ((ctx->seen & SHMEM_SEEN_BLOCKS) && ctx->blocks) {
if (!sbinfo->max_blocks) {
err = "Cannot retroactively limit size";
_
Patches currently in -mm which might be from luomeng12@xxxxxxxxxx are
tmpfs-fix-undefined-behaviour-in-shmem_reconfigure.patch
