Commit 92fdd98c authored by Al Viro's avatar Al Viro Committed by Steven Rostedt
Browse files

tracing: Fix buggered tee(2) on tracing_pipe

In kernel/trace/trace.c we have this:
static void tracing_pipe_buf_release(struct pipe_inode_info *pipe,
                                     struct pipe_buffer *buf)
static const struct pipe_buf_operations tracing_pipe_buf_ops = {
        .can_merge              = 0,
        .map                    = generic_pipe_buf_map,
        .unmap                  = generic_pipe_buf_unmap,
        .confirm                = generic_pipe_buf_confirm,
        .release                = tracing_pipe_buf_release,
        .steal                  = generic_pipe_buf_steal,
        .get                    = generic_pipe_buf_get,
void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)

and I don't see anything that would've prevented tee(2) called on the pipe
that got stuff spliced into it from that sucker.  ->ops->get() will be
called, then buf gets copied into target pipe's ->bufs[] and eventually
readers get to both copies of the buffer.  With
	look at that page
	look at that page
which is not a good thing, to put it mildly.  AFAICS, that ought to use
the normal generic_pipe_buf_release() (aka page_cache_release(buf->page)),
shouldn't it?

 SDR - As trace_pipe just allocates the page with alloc_page(GFP_KERNEL),
  and doesn't do anything special with it (no LRU logic). The __free_page()
  should be fine, as it wont actually free a page with reference count.
  Maybe there's a chance to leak memory? Anyway, This change is at a minimum
  good for being symmetric with generic_pipe_buf_get, it is fine to add.
Signed-off-by: default avatarAl Viro <>
[ SDR - Removed no longer used tracing_pipe_buf_release ]
Signed-off-by: default avatarSteven Rostedt <>
parent dced341b
......@@ -4243,12 +4243,6 @@ tracing_read_pipe(struct file *filp, char __user *ubuf,
return sret;
static void tracing_pipe_buf_release(struct pipe_inode_info *pipe,
struct pipe_buffer *buf)
static void tracing_spd_release_pipe(struct splice_pipe_desc *spd,
unsigned int idx)
......@@ -4260,7 +4254,7 @@ static const struct pipe_buf_operations tracing_pipe_buf_ops = {
.map = generic_pipe_buf_map,
.unmap = generic_pipe_buf_unmap,
.confirm = generic_pipe_buf_confirm,
.release = tracing_pipe_buf_release,
.release = generic_pipe_buf_release,
.steal = generic_pipe_buf_steal,
.get = generic_pipe_buf_get,
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