diff --git a/debian/changelog b/debian/changelog index 81db53648..34545147c 100644 --- a/debian/changelog +++ b/debian/changelog @@ -1110,6 +1110,7 @@ linux (4.19.37-1) UNRELEASED; urgency=medium - aio: keep io_event in aio_kiocb - aio: store event at final iocb_put() - Fix aio_poll() races + * tracing: Fix buffer_ref pipe ops [ YunQiang Su ] * [mips*r6] Re-enable CONFIG_JUMP_LABEL, which has been fixed in upstream. diff --git a/debian/patches/bugfix/all/tracing-fix-buffer_ref-pipe-ops.patch b/debian/patches/bugfix/all/tracing-fix-buffer_ref-pipe-ops.patch new file mode 100644 index 000000000..23f6bda0a --- /dev/null +++ b/debian/patches/bugfix/all/tracing-fix-buffer_ref-pipe-ops.patch @@ -0,0 +1,137 @@ +From: Jann Horn +Date: Thu, 4 Apr 2019 23:59:25 +0200 +Subject: tracing: Fix buffer_ref pipe ops +Origin: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit?id=cffeb9c84d20816a2173e3cfeca210c8bfa8e357 + +commit b987222654f84f7b4ca95b3a55eca784cb30235b upstream. + +This fixes multiple issues in buffer_pipe_buf_ops: + + - The ->steal() handler must not return zero unless the pipe buffer has + the only reference to the page. But generic_pipe_buf_steal() assumes + that every reference to the pipe is tracked by the page's refcount, + which isn't true for these buffers - buffer_pipe_buf_get(), which + duplicates a buffer, doesn't touch the page's refcount. + Fix it by using generic_pipe_buf_nosteal(), which refuses every + attempted theft. It should be easy to actually support ->steal, but the + only current users of pipe_buf_steal() are the virtio console and FUSE, + and they also only use it as an optimization. So it's probably not worth + the effort. + - The ->get() and ->release() handlers can be invoked concurrently on pipe + buffers backed by the same struct buffer_ref. Make them safe against + concurrency by using refcount_t. + - The pointers stored in ->private were only zeroed out when the last + reference to the buffer_ref was dropped. As far as I know, this + shouldn't be necessary anyway, but if we do it, let's always do it. + +Link: http://lkml.kernel.org/r/20190404215925.253531-1-jannh@google.com + +Cc: Ingo Molnar +Cc: Masami Hiramatsu +Cc: Al Viro +Cc: stable@vger.kernel.org +Fixes: 73a757e63114d ("ring-buffer: Return reader page back into existing ring buffer") +Signed-off-by: Jann Horn +Signed-off-by: Steven Rostedt (VMware) +Signed-off-by: Greg Kroah-Hartman +--- + fs/splice.c | 4 ++-- + include/linux/pipe_fs_i.h | 1 + + kernel/trace/trace.c | 28 ++++++++++++++-------------- + 3 files changed, 17 insertions(+), 16 deletions(-) + +--- a/fs/splice.c ++++ b/fs/splice.c +@@ -333,8 +333,8 @@ const struct pipe_buf_operations default + .get = generic_pipe_buf_get, + }; + +-static int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe, +- struct pipe_buffer *buf) ++int generic_pipe_buf_nosteal(struct pipe_inode_info *pipe, ++ struct pipe_buffer *buf) + { + return 1; + } +--- a/include/linux/pipe_fs_i.h ++++ b/include/linux/pipe_fs_i.h +@@ -181,6 +181,7 @@ void free_pipe_info(struct pipe_inode_in + void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *); + int generic_pipe_buf_confirm(struct pipe_inode_info *, struct pipe_buffer *); + int generic_pipe_buf_steal(struct pipe_inode_info *, struct pipe_buffer *); ++int generic_pipe_buf_nosteal(struct pipe_inode_info *, struct pipe_buffer *); + void generic_pipe_buf_release(struct pipe_inode_info *, struct pipe_buffer *); + void pipe_buf_mark_unmergeable(struct pipe_buffer *buf); + +--- a/kernel/trace/trace.c ++++ b/kernel/trace/trace.c +@@ -6800,19 +6800,23 @@ struct buffer_ref { + struct ring_buffer *buffer; + void *page; + int cpu; +- int ref; ++ refcount_t refcount; + }; + ++static void buffer_ref_release(struct buffer_ref *ref) ++{ ++ if (!refcount_dec_and_test(&ref->refcount)) ++ return; ++ ring_buffer_free_read_page(ref->buffer, ref->cpu, ref->page); ++ kfree(ref); ++} ++ + static void buffer_pipe_buf_release(struct pipe_inode_info *pipe, + struct pipe_buffer *buf) + { + struct buffer_ref *ref = (struct buffer_ref *)buf->private; + +- if (--ref->ref) +- return; +- +- ring_buffer_free_read_page(ref->buffer, ref->cpu, ref->page); +- kfree(ref); ++ buffer_ref_release(ref); + buf->private = 0; + } + +@@ -6821,7 +6825,7 @@ static void buffer_pipe_buf_get(struct p + { + struct buffer_ref *ref = (struct buffer_ref *)buf->private; + +- ref->ref++; ++ refcount_inc(&ref->refcount); + } + + /* Pipe buffer operations for a buffer. */ +@@ -6829,7 +6833,7 @@ static const struct pipe_buf_operations + .can_merge = 0, + .confirm = generic_pipe_buf_confirm, + .release = buffer_pipe_buf_release, +- .steal = generic_pipe_buf_steal, ++ .steal = generic_pipe_buf_nosteal, + .get = buffer_pipe_buf_get, + }; + +@@ -6842,11 +6846,7 @@ static void buffer_spd_release(struct sp + struct buffer_ref *ref = + (struct buffer_ref *)spd->partial[i].private; + +- if (--ref->ref) +- return; +- +- ring_buffer_free_read_page(ref->buffer, ref->cpu, ref->page); +- kfree(ref); ++ buffer_ref_release(ref); + spd->partial[i].private = 0; + } + +@@ -6901,7 +6901,7 @@ tracing_buffers_splice_read(struct file + break; + } + +- ref->ref = 1; ++ refcount_set(&ref->refcount, 1); + ref->buffer = iter->trace_buffer->buffer; + ref->page = ring_buffer_alloc_read_page(ref->buffer, iter->cpu_file); + if (IS_ERR(ref->page)) { diff --git a/debian/patches/series b/debian/patches/series index ce60e4117..bc43f3c26 100644 --- a/debian/patches/series +++ b/debian/patches/series @@ -176,6 +176,7 @@ bugfix/all/0011-aio-fold-lookup_kiocb-into-its-sole-caller.patch bugfix/all/0012-aio-keep-io_event-in-aio_kiocb.patch bugfix/all/0013-aio-store-event-at-final-iocb_put.patch bugfix/all/0014-Fix-aio_poll-races.patch +bugfix/all/tracing-fix-buffer_ref-pipe-ops.patch # Fix exported symbol versions bugfix/all/module-disable-matching-missing-version-crc.patch