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由 Jan Kara 提交于
Commit 296291cd (mm: make sendfile(2) killable) fixed an issue where sendfile(2) was doing a lot of tiny writes into a filesystem and thus was unkillable for a long time. However sendfile(2) can be (mis)used to issue lots of writes into arbitrary file descriptor such as evenfd or similar special file descriptors which never hit the standard filesystem write path and thus are still unkillable. E.g. the following example from Dmitry burns CPU for ~16s on my test system without possibility to be killed: 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); There are actually quite a few tests for pending signals in sendfile code however we data to write is always available none of them seems to trigger. So fix the problem by adding a test for pending signal into splice_from_pipe_next() also before the loop waiting for pipe buffers to be available. This should fix all the lockup issues with sendfile of the do-ton-of-tiny-writes nature. CC: stable@vger.kernel.org Reported-by: NDmitry Vyukov <dvyukov@google.com> Signed-off-by: NJan Kara <jack@suse.cz> Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
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