From def6b3ba56b637d58126ef67fc19bab57945fcc4 Mon Sep 17 00:00:00 2001 From: Lachlan McIlroy Date: Thu, 23 Apr 2009 22:18:00 -0400 Subject: [PATCH] xfs_file_last_byte() needs to acquire ilock We had some systems crash with this stack: [] ia64_leave_kernel+0x0/0x280 [] xfs_bmbt_get_startoff+0x0/0x20 [xfs] [] xfs_bmap_last_offset+0x210/0x280 [xfs] [] xfs_file_last_byte+0x70/0x1a0 [xfs] [] xfs_itruncate_start+0xc0/0x1a0 [xfs] [] xfs_inactive_free_eofblocks+0x290/0x460 [xfs] [] xfs_release+0x1b0/0x240 [xfs] [] xfs_file_release+0x70/0xa0 [xfs] [] __fput+0x1a0/0x420 [] fput+0x40/0x60 The problem here is that xfs_file_last_byte() does not acquire the inode lock and can therefore race with another thread that is modifying the extext list. While xfs_bmap_last_offset() is trying to lookup what was the last extent some extents were merged and the extent list shrunk so the index we lookup is now beyond the end of the extent list and potentially in a freed buffer. Signed-off-by: Lachlan McIlroy Reviewed-by: Christoph Hellwig Reviewed-by: Felix Blyakher Signed-off-by: Felix Blyakher --- fs/xfs/xfs_inode.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index e7ae08d1df4..123b20c8cbf 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -1258,8 +1258,10 @@ xfs_file_last_byte( * necessary. */ if (ip->i_df.if_flags & XFS_IFEXTENTS) { + xfs_ilock(ip, XFS_ILOCK_SHARED); error = xfs_bmap_last_offset(NULL, ip, &last_block, XFS_DATA_FORK); + xfs_iunlock(ip, XFS_ILOCK_SHARED); if (error) { last_block = 0; } -- 2.41.0