On Sat, Nov 14, 2020 at 10:02:34PM +0800, Gao Xiang wrote: > Currently, commit e9e2eae89ddb dropped a (int) decoration from > XFS_LITINO(mp), and since sizeof() expression is also involved, > the result of XFS_LITINO(mp) is simply as the size_t type > (commonly unsigned long). > > Considering the expression in xfs_attr_shortform_bytesfit(): > offset = (XFS_LITINO(mp) - bytes) >> 3; > let "bytes" be (int)340, and > "XFS_LITINO(mp)" be (unsigned long)336. > > on 64-bit platform, the expression is > offset = ((unsigned long)336 - (int)340) >> 3 = > (int)(0xfffffffffffffffcUL >> 3) = -1 > > but on 32-bit platform, the expression is > offset = ((unsigned long)336 - (int)340) >> 3 = > (int)(0xfffffffcUL >> 3) = 0x1fffffff > instead. > > so offset becomes a large positive number on 32-bit platform, and > cause xfs_attr_shortform_bytesfit() returns maxforkoff rather than 0. > > Therefore, one result is > "ASSERT(new_size <= XFS_IFORK_SIZE(ip, whichfork));" > > assertion failure in xfs_idata_realloc(), which was also the root > cause of the original bugreport from Dennis, see: > https://bugzilla.redhat.com/show_bug.cgi?id=1894177 > > And it can also be manually triggered with the following commands: > $ touch a; > $ setfattr -n user.0 -v "`seq 0 80`" a; > $ setfattr -n user.1 -v "`seq 0 80`" a > > on 32-bit platform. > > Fix the case in xfs_attr_shortform_bytesfit() by bailing out > "XFS_LITINO(mp) < bytes" in advance suggested by Eric and a misleading > comment together with this bugfix suggested by Darrick. It seems the > other users of XFS_LITINO(mp) are not impacted. > > Fixes: e9e2eae89ddb ("xfs: only check the superblock version for dinode size calculation") > Cc: <stable@xxxxxxxxxxxxxxx> # 5.7+ > Reported-and-tested-by: Dennis Gilmore <dgilmore@xxxxxxxxxx> > Reviewed-by: Christoph Hellwig <hch@xxxxxx> > Signed-off-by: Gao Xiang <hsiangkao@xxxxxxxxxx> Looks good to me, Reviewed-by: Darrick J. Wong <darrick.wong@xxxxxxxxxx> --D > --- > changes since v2: > - collect more tags from the replies of v2; > - refine a comment suggested by Christoph. > > fs/xfs/libxfs/xfs_attr_leaf.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/fs/xfs/libxfs/xfs_attr_leaf.c b/fs/xfs/libxfs/xfs_attr_leaf.c > index bb128db220ac..d6ef69ab1c67 100644 > --- a/fs/xfs/libxfs/xfs_attr_leaf.c > +++ b/fs/xfs/libxfs/xfs_attr_leaf.c > @@ -515,7 +515,7 @@ xfs_attr_copy_value( > *========================================================================*/ > > /* > - * Query whether the requested number of additional bytes of extended > + * Query whether the total requested number of attr fork bytes of extended > * attribute space will be able to fit inline. > * > * Returns zero if not, else the di_forkoff fork offset to be used in the > @@ -535,6 +535,12 @@ xfs_attr_shortform_bytesfit( > int maxforkoff; > int offset; > > + /* > + * Check if the new size could fit at all first: > + */ > + if (bytes > XFS_LITINO(mp)) > + return 0; > + > /* rounded down */ > offset = (XFS_LITINO(mp) - bytes) >> 3; > > -- > 2.18.4 >
