This is a note to let you know that I've just added the patch titled fuse: break infinite loop in fuse_fill_write_pages() to the 3.14-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: fuse-break-infinite-loop-in-fuse_fill_write_pages.patch and it can be found in the queue-3.14 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. >From 3ca8138f014a913f98e6ef40e939868e1e9ea876 Mon Sep 17 00:00:00 2001 From: Roman Gushchin <klamm@xxxxxxxxxxxxxx> Date: Mon, 12 Oct 2015 16:33:44 +0300 Subject: fuse: break infinite loop in fuse_fill_write_pages() 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: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/fuse/file.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -1006,6 +1006,7 @@ static ssize_t fuse_fill_write_pages(str tmp = iov_iter_copy_from_user_atomic(page, ii, offset, bytes); flush_dcache_page(page); + iov_iter_advance(ii, tmp); if (!tmp) { unlock_page(page); page_cache_release(page); @@ -1018,7 +1019,6 @@ static ssize_t fuse_fill_write_pages(str req->page_descs[req->num_pages].length = tmp; req->num_pages++; - iov_iter_advance(ii, tmp); count += tmp; pos += tmp; offset += tmp; Patches currently in stable-queue which might be from klamm@xxxxxxxxxxxxxx are queue-3.14/fuse-break-infinite-loop-in-fuse_fill_write_pages.patch -- 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