The patch titled
Subject: tmpfs: fix the issue that the mount and remount results are inconsistent.
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
tmpfs-fix-the-issue-that-the-mount-and-remount-results-are-inconsistent.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/tmpfs-fix-the-issue-that-the-mount-and-remount-results-are-inconsistent.patch
This patch will later appear in the mm-hotfixes-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: ZhaoLong Wang <wangzhaolong1@xxxxxxxxxx>
Subject: tmpfs: fix the issue that the mount and remount results are inconsistent.
Date: Wed, 29 Jun 2022 20:43:24 +0800
An undefined-behavior issue has not been completely fixed since commit
d14f5efadd84 ("tmpfs: fix undefined-behaviour in shmem_reconfigure()").
In the commit, check in the shmem_reconfigure() is added in remount
process to avoid the Ubsan problem. However, the check is not added to
the mount process. It causes inconsistent results between mount and
remount. The operations to reproduce the problem in user mode as follows:
If nr_blocks is set to 0x8000000000000000, the mounting is successful.
# mount tmpfs /dev/shm/ -t tmpfs -o nr_blocks=0x8000000000000000
However, when -o remount is used, the mount fails because of the
check in the shmem_reconfigure()
# mount tmpfs /dev/shm/ -t tmpfs -o remount,nr_blocks=0x8000000000000000
mount: /dev/shm: mount point not mounted or bad option.
Therefore, add checks in the shmem_parse_one() function and remove the
check in shmem_reconfigure() to avoid this problem.
Link: https://lkml.kernel.org/r/20220629124324.1640807-1-wangzhaolong1@xxxxxxxxxx
Signed-off-by: ZhaoLong Wang <wangzhaolong1@xxxxxxxxxx>
Cc: Luo Meng <luomeng12@xxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Yu Kuai <yukuai3@xxxxxxxxxx>
Cc: Zhihao Cheng <chengzhihao1@xxxxxxxxxx>
Cc: Zhang Yi <yi.zhang@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/shmem.c | 7 ++-----
1 file changed, 2 insertions(+), 5 deletions(-)
--- a/mm/shmem.c~tmpfs-fix-the-issue-that-the-mount-and-remount-results-are-inconsistent
+++ a/mm/shmem.c
@@ -3392,7 +3392,7 @@ static int shmem_parse_one(struct fs_con
break;
case Opt_nr_blocks:
ctx->blocks = memparse(param->string, &rest);
- if (*rest)
+ if (*rest || ctx->blocks > S64_MAX)
goto bad_value;
ctx->seen |= SHMEM_SEEN_BLOCKS;
break;
@@ -3514,10 +3514,7 @@ 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 = "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 wangzhaolong1@xxxxxxxxxx are
tmpfs-fix-the-issue-that-the-mount-and-remount-results-are-inconsistent.patch
