6.12-stable review patch. If anyone has any objections, please let me know.
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From: Pedro Demarchi Gomes pedrodemargomes@gmail.com
[ Upstream commit d1693a7d5a38acf6424235a6070bcf5b186a360d ]
When mounting, sb->s_blocksize is used to read the boot_block without being defined or validated. Set a dummy blocksize before attempting to read the boot_block.
The issue can be triggered with the following syz reproducer:
mkdirat(0xffffffffffffff9c, &(0x7f0000000080)='./file1\x00', 0x0) r4 = openat$nullb(0xffffffffffffff9c, &(0x7f0000000040), 0x121403, 0x0) ioctl$FS_IOC_SETFLAGS(r4, 0x40081271, &(0x7f0000000980)=0x4000) mount(&(0x7f0000000140)=@nullb, &(0x7f0000000040)='./cgroup\x00', &(0x7f0000000000)='ntfs3\x00', 0x2208004, 0x0) syz_clone(0x88200200, 0x0, 0x0, 0x0, 0x0, 0x0)
Here, the ioctl sets the bdev block size to 16384. During mount, get_tree_bdev_flags() calls sb_set_blocksize(sb, block_size(bdev)), but since block_size(bdev) > PAGE_SIZE, sb_set_blocksize() leaves sb->s_blocksize at zero.
Later, ntfs_init_from_boot() attempts to read the boot_block while sb->s_blocksize is still zero, which triggers the bug.
Reported-by: syzbot+f4f84b57a01d6b8364ad@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=f4f84b57a01d6b8364ad Signed-off-by: Pedro Demarchi Gomes pedrodemargomes@gmail.com [almaz.alexandrovich@paragon-software.com: changed comment style, added return value handling] Signed-off-by: Konstantin Komarov almaz.alexandrovich@paragon-software.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/ntfs3/super.c | 5 +++++ 1 file changed, 5 insertions(+)
diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c index 6a0f6b0a3ab2a..89d126c155c7d 100644 --- a/fs/ntfs3/super.c +++ b/fs/ntfs3/super.c @@ -892,6 +892,11 @@ static int ntfs_init_from_boot(struct super_block *sb, u32 sector_size,
sbi->volume.blocks = dev_size >> PAGE_SHIFT;
+ /* Set dummy blocksize to read boot_block. */ + if (!sb_min_blocksize(sb, PAGE_SIZE)) { + return -EINVAL; + } + read_boot: bh = ntfs_bread(sb, boot_block); if (!bh)