From: Eric Sandeen <sandeen@xxxxxxxxxxx> 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit 4dfce57db6354603641132fac3c887614e3ebe81 upstream. There have been several reports over the years of NULL pointer dereferences in xfs_trans_log_inode during xfs_fsr processes, when the process is doing an fput and tearing down extents on the temporary inode, something like: BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 PID: 29439 TASK: ffff880550584fa0 CPU: 6 COMMAND: "xfs_fsr" [exception RIP: xfs_trans_log_inode+0x10] #9 [ffff8800a57bbbe0] xfs_bunmapi at ffffffffa037398e [xfs] As it turns out, this is because the i_itemp pointer, along with the d_ops pointer, has been overwritten with zeros when we tear down the extents during truncate. When the in-core inode fork on the temporary inode used by xfs_fsr was originally set up during the extent swap, we mistakenly looked at di_nextents to determine whether all extents fit inline, but this misses extents generated by speculative preallocation; we should be using if_bytes instead. This mistake corrupts the in-memory inode, and code in xfs_iext_remove_inline eventually gets bad inputs, causing it to memmove and memset incorrect ranges; this became apparent because the two values in ifp->if_u2.if_inline_ext[1] contained what should have been in d_ops and i_itemp; they were memmoved due to incorrect array indexing and then the original locations were zeroed with memset, again due to an array overrun. Fix this by properly using i_df.if_bytes to determine the number of extents, not di_nextents. Thanks to dchinner for looking at this with me and spotting the root cause. [nborisov: Backported to 3.12] Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx> Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx> Signed-off-by: Dave Chinner <david@xxxxxxxxxxxxx> Signed-off-by: Nikolay Borisov <nborisov@xxxxxxxx> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx> --- fs/xfs/xfs_bmap_util.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/fs/xfs/xfs_bmap_util.c b/fs/xfs/xfs_bmap_util.c index 42cb2f3ea51f..51df0cf5ea62 100644 --- a/fs/xfs/xfs_bmap_util.c +++ b/fs/xfs/xfs_bmap_util.c @@ -1776,6 +1776,7 @@ xfs_swap_extents( xfs_trans_t *tp; xfs_bstat_t *sbp = &sxp->sx_stat; xfs_ifork_t *tempifp, *ifp, *tifp; + xfs_extnum_t nextents; int src_log_flags, target_log_flags; int error = 0; int aforkblks = 0; @@ -1984,7 +1985,8 @@ xfs_swap_extents( * pointer. Otherwise it's already NULL or * pointing to the extent. */ - if (ip->i_d.di_nextents <= XFS_INLINE_EXTS) { + nextents = ip->i_df.if_bytes / (uint)sizeof(xfs_bmbt_rec_t); + if (nextents <= XFS_INLINE_EXTS) { ifp->if_u1.if_extents = ifp->if_u2.if_inline_ext; } @@ -2003,7 +2005,8 @@ xfs_swap_extents( * pointer. Otherwise it's already NULL or * pointing to the extent. */ - if (tip->i_d.di_nextents <= XFS_INLINE_EXTS) { + nextents = tip->i_df.if_bytes / (uint)sizeof(xfs_bmbt_rec_t); + if (nextents <= XFS_INLINE_EXTS) { tifp->if_u1.if_extents = tifp->if_u2.if_inline_ext; } -- 2.12.2