Fix a potential infinite loop in extract_user_to_sg()

Fix extract_user_to_sg() so that it will break out of the loop if
iov_iter_extract_pages() returns 0 rather than looping around forever.

[Note that I've included two fixes lines as the function got moved to a
different file and renamed]

Fixes: 85dd2c8ff368 ("netfs: Add a function to extract a UBUF or IOVEC into a BVEC iterator")
Fixes: f5f82cd18732 ("Move netfs_extract_iter_to_sg() to lib/scatterlist.c")
Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: Steve French <sfrench@samba.org>
cc: Herbert Xu <herbert@gondor.apana.org.au>
cc: netfs@lists.linux.dev
Link: https://lore.kernel.org/r/1967121.1714034372@warthog.procyon.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/lib/scatterlist.c b/lib/scatterlist.c
index 68b45c82c37a6981bb72cc79ab4c4fcac8e2e489..7bc2220fea805855fadd0a1ed347ea2b9195e9e9 100644 (file)
--- a/lib/scatterlist.c
+++ b/lib/scatterlist.c
@@ -1124,7 +1124,7 @@ static ssize_t extract_user_to_sg(struct iov_iter *iter,
        do {
                res = iov_iter_extract_pages(iter, &pages, maxsize, sg_max,
                                             extraction_flags, &off);
-               if (res < 0)
+               if (res <= 0)
                        goto failed;
 
                len = res;