From: Dave Chinner Date: Fri, 3 Sep 2010 02:19:33 +0000 (+1000) Subject: xfs: prevent 32bit overflow in space reservation X-Git-Url: http://git.lede-project.org./?a=commitdiff_plain;h=72656c46f50b8dfe50e15793692982e636e3df20;p=openwrt%2Fstaging%2Fblogic.git xfs: prevent 32bit overflow in space reservation If we attempt to preallocate more than 2^32 blocks of space in a single syscall, the transaction block reservation will overflow leading to a hangs in the superblock block accounting code. This is trivially reproduced with xfs_io. Fix the problem by capping the allocation reservation to the maximum number of blocks a single xfs_bmapi() call can allocate (2^21 blocks). Signed-off-by: Dave Chinner Reviewed-by: Christoph Hellwig --- diff --git a/fs/xfs/xfs_vnodeops.c b/fs/xfs/xfs_vnodeops.c index 66d585c6917c..4c7c7bfb2b2f 100644 --- a/fs/xfs/xfs_vnodeops.c +++ b/fs/xfs/xfs_vnodeops.c @@ -2299,15 +2299,22 @@ xfs_alloc_file_space( e = allocatesize_fsb; } + /* + * The transaction reservation is limited to a 32-bit block + * count, hence we need to limit the number of blocks we are + * trying to reserve to avoid an overflow. We can't allocate + * more than @nimaps extents, and an extent is limited on disk + * to MAXEXTLEN (21 bits), so use that to enforce the limit. + */ + resblks = min_t(xfs_fileoff_t, (e - s), (MAXEXTLEN * nimaps)); if (unlikely(rt)) { - resrtextents = qblocks = (uint)(e - s); + resrtextents = qblocks = resblks; resrtextents /= mp->m_sb.sb_rextsize; resblks = XFS_DIOSTRAT_SPACE_RES(mp, 0); quota_flag = XFS_QMOPT_RES_RTBLKS; } else { resrtextents = 0; - resblks = qblocks = \ - XFS_DIOSTRAT_SPACE_RES(mp, (uint)(e - s)); + resblks = qblocks = XFS_DIOSTRAT_SPACE_RES(mp, resblks); quota_flag = XFS_QMOPT_RES_REGBLKS; }