diff options
author | Roman Gushchin <klamm@yandex-team.ru> | 2015-10-12 09:33:44 -0400 |
---|---|---|
committer | Miklos Szeredi <miklos@szeredi.hu> | 2015-11-10 04:32:37 -0500 |
commit | 3ca8138f014a913f98e6ef40e939868e1e9ea876 (patch) | |
tree | f8958826e39c9270e3786f773f9720114177770e /fs/fuse/file.c | |
parent | 2c5816b4beccc8ba709144539f6fdd764f8fa49c (diff) |
fuse: break infinite loop in fuse_fill_write_pages()
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@linux-foundation.org>
Cc: Maxim Patlasov <mpatlasov@parallels.com>
Cc: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Roman Gushchin <klamm@yandex-team.ru>
Signed-off-by: Miklos Szeredi <miklos@szeredi.hu>
Fixes: ea9b9907b82a ("fuse: implement perform_write")
Cc: <stable@vger.kernel.org>
Diffstat (limited to 'fs/fuse/file.c')
-rw-r--r-- | fs/fuse/file.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/fuse/file.c b/fs/fuse/file.c index f523f2f04c19..195476a24148 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, | |||
1049 | tmp = iov_iter_copy_from_user_atomic(page, ii, offset, bytes); | 1049 | tmp = iov_iter_copy_from_user_atomic(page, ii, offset, bytes); |
1050 | flush_dcache_page(page); | 1050 | flush_dcache_page(page); |
1051 | 1051 | ||
1052 | iov_iter_advance(ii, tmp); | ||
1052 | if (!tmp) { | 1053 | if (!tmp) { |
1053 | unlock_page(page); | 1054 | unlock_page(page); |
1054 | page_cache_release(page); | 1055 | page_cache_release(page); |
@@ -1061,7 +1062,6 @@ static ssize_t fuse_fill_write_pages(struct fuse_req *req, | |||
1061 | req->page_descs[req->num_pages].length = tmp; | 1062 | req->page_descs[req->num_pages].length = tmp; |
1062 | req->num_pages++; | 1063 | req->num_pages++; |
1063 | 1064 | ||
1064 | iov_iter_advance(ii, tmp); | ||
1065 | count += tmp; | 1065 | count += tmp; |
1066 | pos += tmp; | 1066 | pos += tmp; |
1067 | offset += tmp; | 1067 | offset += tmp; |