diff options
authorTorsten Hilbrich <>2016-06-24 14:50:18 -0700
committerLinus Torvalds <>2016-06-24 17:23:52 -0700
commit63d2f95d63396059200c391ca87161897b99e74a (patch)
parent74070542099c66d87aebeacd7b54dc0e8b6a73f9 (diff)
fs/nilfs2: fix potential underflow in call to crc32_le
The value `bytes' comes from the filesystem which is about to be mounted. We cannot trust that the value is always in the range we expect it to be. Check its value before using it to calculate the length for the crc32_le call. It value must be larger (or equal) sumoff + 4. This fixes a kernel bug when accidentially mounting an image file which had the nilfs2 magic value 0x3434 at the right offset 0x406 by chance. The bytes 0x01 0x00 were stored at 0x408 and were interpreted as a s_bytes value of 1. This caused an underflow when substracting sumoff + 4 (20) in the call to crc32_le. BUG: unable to handle kernel paging request at ffff88021e600000 IP: crc32_le+0x36/0x100 ... Call Trace: nilfs_valid_sb.part.5+0x52/0x60 [nilfs2] nilfs_load_super_block+0x142/0x300 [nilfs2] init_nilfs+0x60/0x390 [nilfs2] nilfs_mount+0x302/0x520 [nilfs2] mount_fs+0x38/0x160 vfs_kern_mount+0x67/0x110 do_mount+0x269/0xe00 SyS_mount+0x9f/0x100 entry_SYSCALL_64_fastpath+0x16/0x71 Link: Signed-off-by: Torsten Hilbrich <> Tested-by: Torsten Hilbrich <> Signed-off-by: Ryusuke Konishi <> Cc: <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/nilfs2/the_nilfs.c b/fs/nilfs2/the_nilfs.c
index 809bd2de7ad0..e9fd241b9a0a 100644
--- a/fs/nilfs2/the_nilfs.c
+++ b/fs/nilfs2/the_nilfs.c
@@ -439,7 +439,7 @@ static int nilfs_valid_sb(struct nilfs_super_block *sbp)
if (!sbp || le16_to_cpu(sbp->s_magic) != NILFS_SUPER_MAGIC)
return 0;
bytes = le16_to_cpu(sbp->s_bytes);
- if (bytes > BLOCK_SIZE)
+ if (bytes < sumoff + 4 || bytes > BLOCK_SIZE)
return 0;
crc = crc32_le(le32_to_cpu(sbp->s_crc_seed), (unsigned char *)sbp,