mm, fs: check for fatal signals in do_generic_file_read()

do_generic_file_read() can be told to perform a large request from
userspace.  If the system is under OOM and the reading task is the OOM
victim then it has an access to memory reserves and finishing the full
request can lead to the full memory depletion which is dangerous.  Make
sure we rather go with a short read and allow the killed task to
terminate.

Link: http://lkml.kernel.org/r/20170201092706.9966-3-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko@suse.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/filemap.c b/mm/filemap.c
index b772a33ef640ab0d6770bb3d249a6fe6f16eeebc..3f9afded581be1a013bda4db2c0ec3a721323364 100644 (file)
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1791,6 +1791,11 @@ static ssize_t do_generic_file_read(struct file *filp, loff_t *ppos,
 
                cond_resched();
 find_page:
+               if (fatal_signal_pending(current)) {
+                       error = -EINTR;
+                       goto out;
+               }
+
                page = find_get_page(mapping, index);
                if (!page) {
                        page_cache_sync_readahead(mapping,