diff options
| author | Phillip Lougher <phillip@squashfs.org.uk> | 2025-04-09 03:47:47 +0100 |
|---|---|---|
| committer | Andrew Morton <akpm@linux-foundation.org> | 2025-05-11 17:54:07 -0700 |
| commit | 734aa85390ea693bb7eaf2240623d41b03705c84 (patch) | |
| tree | 1c0a158bdfb7f7b6879d6eedd6d3cc12e9e2dfae | |
| parent | fe6f600c43e0931f4fb5e1debb2311b7a6ebabd8 (diff) | |
Squashfs: check return result of sb_min_blocksize
Syzkaller reports an "UBSAN: shift-out-of-bounds in squashfs_bio_read" bug.
Syzkaller forks multiple processes which after mounting the Squashfs
filesystem, issues an ioctl("/dev/loop0", LOOP_SET_BLOCK_SIZE, 0x8000).
Now if this ioctl occurs at the same time another process is in the
process of mounting a Squashfs filesystem on /dev/loop0, the failure
occurs. When this happens the following code in squashfs_fill_super()
fails.
----
msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE);
msblk->devblksize_log2 = ffz(~msblk->devblksize);
----
sb_min_blocksize() returns 0, which means msblk->devblksize is set to 0.
As a result, ffz(~msblk->devblksize) returns 64, and msblk->devblksize_log2
is set to 64.
This subsequently causes the
UBSAN: shift-out-of-bounds in fs/squashfs/block.c:195:36
shift exponent 64 is too large for 64-bit type 'u64' (aka
'unsigned long long')
This commit adds a check for a 0 return by sb_min_blocksize().
Link: https://lkml.kernel.org/r/20250409024747.876480-1-phillip@squashfs.org.uk
Fixes: 0aa666190509 ("Squashfs: super block operations")
Reported-by: syzbot+65761fc25a137b9c8c6e@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/67f0dd7a.050a0220.0a13.0230.GAE@google.com/
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
| -rw-r--r-- | fs/squashfs/super.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/fs/squashfs/super.c b/fs/squashfs/super.c index 67c55fe32ce8..992ea0e37257 100644 --- a/fs/squashfs/super.c +++ b/fs/squashfs/super.c @@ -202,6 +202,11 @@ static int squashfs_fill_super(struct super_block *sb, struct fs_context *fc) msblk->panic_on_errors = (opts->errors == Opt_errors_panic); msblk->devblksize = sb_min_blocksize(sb, SQUASHFS_DEVBLK_SIZE); + if (!msblk->devblksize) { + errorf(fc, "squashfs: unable to set blocksize\n"); + return -EINVAL; + } + msblk->devblksize_log2 = ffz(~msblk->devblksize); mutex_init(&msblk->meta_index_mutex); |