Messages in this thread Patch in this message | | | From | Roman Gushchin <> | Subject | [PATCH] fuse: break infinite loop in fuse_fill_write_pages() | Date | Mon, 21 Sep 2015 13:02:53 +0300 |
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I got a report about unkillable task eating CPU. Thge 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").
Signed-off-by: Roman Gushchin <klamm@yandex-team.ru> Cc: Miklos Szeredi <miklos@szeredi.hu> --- 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 f523f2f..195476a 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -1049,6 +1049,7 @@ static ssize_t fuse_fill_write_pages(struct fuse_req *req, 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); @@ -1061,7 +1062,6 @@ 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; -- 2.4.3
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