Commit c2489e07 authored Nov 23, 2015 by Jan Kara Committed by Al Viro Nov 23, 2015

vfs: Avoid softlockups with sendfile(2)



The following test program from Dmitry can cause softlockups or RCU
stalls as it copies 1GB from tmpfs into eventfd and we don't have any
scheduling point at that path in sendfile(2) implementation:

        int r1 = eventfd(0, 0);
        int r2 = memfd_create("", 0);
        unsigned long n = 1<<30;
        fallocate(r2, 0, 0, n);
        sendfile(r1, r2, 0, n);

Add cond_resched() into __splice_from_pipe() to fix the problem.

CC: Dmitry Vyukov <dvyukov@google.com>
CC: stable@vger.kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

parent c725bfce

fs/splice.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -891,6 +891,7 @@ ssize_t __splice_from_pipe(struct pipe_inode_info pipe, struct splice_desc sd,

		splice_from_pipe_begin(sd);
		do {
		cond_resched();
		ret = splice_from_pipe_next(pipe, sd);
		if (ret > 0)
		ret = splice_from_pipe_feed(pipe, sd, actor);

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