3.13.11-ckt33 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Roman Gushchin <klamm@xxxxxxxxxxxxxx> commit 3ca8138f014a913f98e6ef40e939868e1e9ea876 upstream. I got a report about unkillable task eating CPU. Further investigation shows, that the problem is in the fuse_fill_write_pages() function. If iov's first segment has zero length, we get an infinite loop, because we never reach iov_iter_advance() call. Fix this by calling iov_iter_advance() before repeating an attempt to copy data from userspace. A similar problem is described in 124d3b7041f ("fix writev regression: pan hanging unkillable and un-straceable"). If zero-length segmend is followed by segment with invalid address, iov_iter_fault_in_readable() checks only first segment (zero-length), iov_iter_copy_from_user_atomic() skips it, fails at second and returns zero -> goto again without skipping zero-length segment. Patch calls iov_iter_advance() before goto again: we'll skip zero-length segment at second iteraction and iov_iter_fault_in_readable() will detect invalid address. Special thanks to Konstantin Khlebnikov, who helped a lot with the commit description. Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Cc: Maxim Patlasov <mpatlasov@xxxxxxxxxxxxx> Cc: Konstantin Khlebnikov <khlebnikov@xxxxxxxxxxxxxx> Signed-off-by: Roman Gushchin <klamm@xxxxxxxxxxxxxx> Signed-off-by: Miklos Szeredi <miklos@xxxxxxxxxx> Fixes: ea9b9907b82a ("fuse: implement perform_write") Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx> --- fs/fuse/file.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 7e70506..f536000 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -993,6 +993,7 @@ static ssize_t fuse_fill_write_pages(struct fuse_req *req, mark_page_accessed(page); + iov_iter_advance(ii, tmp); if (!tmp) { unlock_page(page); page_cache_release(page); @@ -1005,7 +1006,6 @@ static ssize_t fuse_fill_write_pages(struct fuse_req *req, req->page_descs[req->num_pages].length = tmp; req->num_pages++; - iov_iter_advance(ii, tmp); count += tmp; pos += tmp; offset += tmp; -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html