diff options
author | Roman Gushchin <klamm@yandex-team.ru> | 2015-10-12 16:33:44 +0300 |
---|---|---|
committer | Luis Henriques <luis.henriques@canonical.com> | 2016-01-11 10:50:14 +0000 |
commit | e595f1d352d3531f5295b45ce7feab29d483ec69 (patch) | |
tree | b9a47460f53aefc96086d0bc26c3c5983b563d40 /fs/fuse | |
parent | c5305f04d7b78f16586a5fbce2690c57a855f5cf (diff) | |
download | linux-stable-e595f1d352d3531f5295b45ce7feab29d483ec69.tar.gz linux-stable-e595f1d352d3531f5295b45ce7feab29d483ec69.tar.bz2 linux-stable-e595f1d352d3531f5295b45ce7feab29d483ec69.zip |
fuse: break infinite loop in fuse_fill_write_pages()
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@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")
Signed-off-by: Luis Henriques <luis.henriques@canonical.com>
Diffstat (limited to 'fs/fuse')
-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 caa8d95b24e8..e2a2c14a90ee 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -1088,6 +1088,7 @@ 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); @@ -1100,7 +1101,6 @@ 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; |