From 0ebf7f10d67a70e120f365018f1c5fce9ddc567d Mon Sep 17 00:00:00 2001 From: Al Viro Date: Mon, 23 Nov 2015 21:11:08 -0500 Subject: [PATCH 1/3] fix sysvfs symlinks The thing got broken back in 2002 - sysvfs does *not* have inline symlinks; even short ones have bodies stored in the first block of file. sysv_symlink() handles that correctly; unfortunately, attempting to look an existing symlink up will end up confusing them for inline symlinks, and interpret the block number containing the body as the body itself. Nobody has noticed until now, which says something about the level of testing sysvfs gets ;-/ Cc: stable@vger.kernel.org # all of them, not that anyone cared Signed-off-by: Al Viro --- fs/sysv/inode.c | 11 ++--------- 1 file changed, 2 insertions(+), 9 deletions(-) diff --git a/fs/sysv/inode.c b/fs/sysv/inode.c index 590ad9206e3f..02fa1dcc5969 100644 --- a/fs/sysv/inode.c +++ b/fs/sysv/inode.c @@ -162,15 +162,8 @@ void sysv_set_inode(struct inode *inode, dev_t rdev) inode->i_fop = &sysv_dir_operations; inode->i_mapping->a_ops = &sysv_aops; } else if (S_ISLNK(inode->i_mode)) { - if (inode->i_blocks) { - inode->i_op = &sysv_symlink_inode_operations; - inode->i_mapping->a_ops = &sysv_aops; - } else { - inode->i_op = &simple_symlink_inode_operations; - inode->i_link = (char *)SYSV_I(inode)->i_data; - nd_terminate_link(inode->i_link, inode->i_size, - sizeof(SYSV_I(inode)->i_data) - 1); - } + inode->i_op = &sysv_symlink_inode_operations; + inode->i_mapping->a_ops = &sysv_aops; } else init_special_inode(inode, inode->i_mode, rdev); } From c725bfce7968009756ed2836a8cd7ba4dc163011 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Mon, 23 Nov 2015 13:09:50 +0100 Subject: [PATCH 2/3] vfs: Make sendfile(2) killable even better 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 --- fs/splice.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/fs/splice.c b/fs/splice.c index 801c21cd77fe..22adbbe51e52 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -809,6 +809,13 @@ static int splice_from_pipe_feed(struct pipe_inode_info *pipe, struct splice_des */ static int splice_from_pipe_next(struct pipe_inode_info *pipe, struct splice_desc *sd) { + /* + * Check for signal early to make process killable when there are + * always buffers available + */ + if (signal_pending(current)) + return -ERESTARTSYS; + while (!pipe->nrbufs) { if (!pipe->writers) return 0; From c2489e07c0a71a56fb2c84bc0ee66cddfca7d068 Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Mon, 23 Nov 2015 13:09:51 +0100 Subject: [PATCH 3/3] 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 CC: stable@vger.kernel.org Signed-off-by: Jan Kara Signed-off-by: Al Viro --- fs/splice.c | 1 + 1 file changed, 1 insertion(+) diff --git a/fs/splice.c b/fs/splice.c index 22adbbe51e52..4cf700d50b40 100644 --- a/fs/splice.c +++ b/fs/splice.c @@ -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);