From: David Howells dhowells@redhat.com
[ Upstream commit 17eabd42560f4636648ad65ba5b20228071e2363 ]
In AFS, a directory is handled as a file that the client downloads and parses locally for the purposes of performing lookup and getdents operations. The in-kernel afs filesystem has a number of functions that do this.
A directory file is arranged as a series of 2K blocks divided into 32-byte slots, where a directory entry occupies one or more slots, plus each block starts with one or more metadata blocks.
When parsing a block, if the last slots are occupied by a dirent that occupies more than a single slot and the file position points at a slot that's not the initial one, the logic in afs_dir_iterate_block() that skips over it won't advance the file pointer to the end of it. This will cause an infinite loop in getdents() as it will keep retrying that block and failing to advance beyond the final entry.
Fix this by advancing the file pointer if the next entry will be beyond it when we skip a block.
This was found by the generic/676 xfstest but can also be triggered with something like:
~/xfstests-dev/src/t_readdir_3 /xfstest.test/z 4000 1
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: David Howells dhowells@redhat.com Reviewed-by: Marc Dionne marc.dionne@auristor.com Tested-by: Marc Dionne marc.dionne@auristor.com cc: linux-afs@lists.infradead.org Link: http://lore.kernel.org/r/165391973497.110268.2939296942213894166.stgit@warth... Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- fs/afs/dir.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/fs/afs/dir.c b/fs/afs/dir.c index da9b4f8577a1..7f1cb3b73874 100644 --- a/fs/afs/dir.c +++ b/fs/afs/dir.c @@ -462,8 +462,11 @@ static int afs_dir_iterate_block(struct afs_vnode *dvnode, }
/* skip if starts before the current position */ - if (offset < curr) + if (offset < curr) { + if (next > curr) + ctx->pos = blkoff + next * sizeof(union afs_xdr_dirent); continue; + }
/* found the next entry */ if (!dir_emit(ctx, dire->u.name, nlen,