[PATCH 2/3] xfs: verify extent size hint is valid in inode verifier

Dave Chinner
2018-06-05T02:43:22Z

From: Dave Chinner <dchinner@redhat.com>

There are rules for vald extent size hints. We enforce them when
applications set them, but fuzzers violate those rules and that
screws us over.

This results in alignment assertion failures when setting up
allocations such as this in direct IO:

XFS: Assertion failed: ap->length, file: fs/xfs/libxfs/xfs_bmap.c, line: 3432
....
Call Trace:
xfs_bmap_btalloc+0x415/0x910
xfs_bmapi_write+0x71c/0x12e0
xfs_iomap_write_direct+0x2a9/0x420
xfs_file_iomap_begin+0x4dc/0xa70
iomap_apply+0x43/0x100
iomap_file_buffered_write+0x62/0x90
xfs_file_buffered_aio_write+0xba/0x300
__vfs_write+0xd5/0x150
vfs_write+0xb6/0x180
ksys_write+0x45/0xa0
do_syscall_64+0x5a/0x180
entry_SYSCALL_64_after_hwframe+0x49/0xbe

And from xfs_db:

core.extsize = 10380288

Which is not an integer multiple of the block size, and so violates
Rule #7 for setting extent size hints. Validate extent size hint
rules in the inode verifier to catch this.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
---
fs/xfs/libxfs/xfs_inode_buf.c | 7 +++++++
1 file changed, 7 insertions(+)

diff --git a/fs/xfs/libxfs/xfs_inode_buf.c b/fs/xfs/libxfs/xfs_inode_buf.c
index f5fff1ccb61d..be197c91307b 100644
--- a/fs/xfs/libxfs/xfs_inode_buf.c
+++ b/fs/xfs/libxfs/xfs_inode_buf.c
@@ -385,6 +385,7 @@ xfs_dinode_verify(
xfs_ino_t ino,
struct xfs_dinode *dip)
{
+ xfs_failaddr_t fa;
uint16_t mode;
uint16_t flags;
uint64_t flags2;
@@ -501,6 +502,12 @@ xfs_dinode_verify(
return __this_address;
}

+ /* extent size hint validation */
+ fa = xfs_inode_validate_extsize(mp, be32_to_cpu(dip->di_extsize),
+ mode, be32_to_cpu(dip->di_flags));
+ if (fa)
+ return fa;
+
/* only version 3 or greater inodes are extensively verified here */
if (dip->di_version < 3)
return NULL;
--
2.17.0