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>
[ The context change is due to the commit c39de951282d
("fs/ntfs3: Improve alternative boot processing")
in v6.8 which is irrelevant to the logic of this patch. ]
Signed-off-by: Rahul Sharma <black.hawk@163.com>
---
fs/ntfs3/super.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/fs/ntfs3/super.c b/fs/ntfs3/super.c
index 674a16c0c66b..7cf52b70987b 100644
--- a/fs/ntfs3/super.c
+++ b/fs/ntfs3/super.c
@@ -693,6 +693,11 @@ 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;
+ }
+
bh = ntfs_bread(sb, 0);
if (!bh)
return -EIO;
--
2.34.1