kernel.git/fs/splice.c, branch linux-3.18.y

vfs: Make sendfile(2) killable even better

2018-11-10T15:39:20Z

[ Upstream commit c725bfce7968009756ed2836a8cd7ba4dc163011 ] Commit 296291cdd162 (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: Dmitry Vyukov Signed-off-by: Jan Kara Signed-off-by: Al Viro Signed-off-by: Sasha Levin

splice: handle zero nr_pages in splice_to_pipe()

2016-04-18T12:49:36Z

[ Upstream commit d6785d9152147596f60234157da2b02540c3e60f ] Running the following command: busybox cat /sys/kernel/debug/tracing/trace_pipe > /dev/null with any tracing enabled pretty very quickly leads to various NULL pointer dereferences and VM BUG_ON()s, such as these: BUG: unable to handle kernel NULL pointer dereference at 0000000000000020 IP: [] generic_pipe_buf_release+0xc/0x40 Call Trace: [] splice_direct_to_actor+0x143/0x1e0 [] ? generic_pipe_buf_nosteal+0x10/0x10 [] do_splice_direct+0x8f/0xb0 [] do_sendfile+0x199/0x380 [] SyS_sendfile64+0x90/0xa0 [] entry_SYSCALL_64_fastpath+0x12/0x6d page dumped because: VM_BUG_ON_PAGE(atomic_read(&page->_count) == 0) kernel BUG at include/linux/mm.h:367! invalid opcode: 0000 [#1] PREEMPT SMP DEBUG_PAGEALLOC RIP: [] generic_pipe_buf_release+0x3c/0x40 Call Trace: [] splice_direct_to_actor+0x143/0x1e0 [] ? generic_pipe_buf_nosteal+0x10/0x10 [] do_splice_direct+0x8f/0xb0 [] do_sendfile+0x199/0x380 [] SyS_sendfile64+0x90/0xa0 [] tracesys_phase2+0x84/0x89 (busybox's cat uses sendfile(2), unlike the coreutils version) This is because tracing_splice_read_pipe() can call splice_to_pipe() with spd->nr_pages == 0. spd_pages underflows in splice_to_pipe() and we fill the page pointers and the other fields of the pipe_buffers with garbage. All other callers of splice_to_pipe() avoid calling it when nr_pages == 0, and we could make tracing_splice_read_pipe() do that too, but it seems reasonable to have splice_to_page() handle this condition gracefully. Cc: stable@vger.kernel.org Signed-off-by: Rabin Vincent Reviewed-by: Christoph Hellwig Signed-off-by: Al Viro Signed-off-by: Sasha Levin

vfs: export do_splice_direct() to modules

2014-10-23T22:14:35Z

Export do_splice_direct() to modules. Needed by overlay filesystem. Signed-off-by: Miklos Szeredi

Merge commit '9f12600fe425bc28f0ccba034a77783c09c15af4' into for-linus

2014-06-12T04:28:09Z

Backmerge of dcache.c changes from mainline. It's that, or complete rebase... Conflicts: fs/splice.c Signed-off-by: Al Viro

kill generic_file_splice_write()

2014-06-12T04:21:13Z

no callers left Signed-off-by: Al Viro

fs/splice.c: remove unneeded exports

2014-06-12T04:21:11Z

ocfs2 was using a bunch of splice.c guts... Signed-off-by: Al Viro

->splice_write() via ->write_iter()

2014-06-12T04:18:51Z

iter_file_splice_write() - a ->splice_write() instance that gathers the pipe buffers, builds a bio_vec-based iov_iter covering those and feeds it to ->write_iter(). A bunch of simple cases coverted to that... [AV: fixed the braino spotted by Cyrill] Signed-off-by: Al Viro

vfs: fix vmplice_to_user()

2014-05-28T05:54:52Z

Commit 6130f5315ee8 "switch vmsplice_to_user() to copy_page_to_iter()" in v3.15-rc1 broke vmsplice(2). This patch fixes two bugs: - count is not initialized to a proper value, which resulted in no data being copied - if rw_copy_check_uvector() returns negative then the iov might be leaked. Tested OK. Signed-off-by: Miklos Szeredi Signed-off-by: Al Viro

start adding the tag to iov_iter

2014-05-06T21:32:49Z

For now, just use the same thing we pass to ->direct_IO() - it's all iovec-based at the moment. Pass it explicitly to iov_iter_init() and account for kvec vs. iovec in there, by the same kludge NFS ->direct_IO() uses. Signed-off-by: Al Viro

switch vmsplice_to_user() to copy_page_to_iter()

2014-04-02T03:19:23Z

I've switched the sanity checks on iovec to rw_copy_check_uvector(); we might need to do a local analog, if any behaviour differences are not actually bugfixes here... Signed-off-by: Al Viro