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author | Al Viro <viro@ZenIV.linux.org.uk> | 2014-01-17 07:53:39 -0500 |
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committer | Steven Rostedt <rostedt@goodmis.org> | 2014-01-19 16:53:13 -0500 |
commit | 92fdd98cf8bdec4d6b0c510e2f073ac4fd059be8 (patch) | |
tree | 0b8a7946835eb969ea2e8fcf335be2f119f696be /Documentation/driver-model | |
parent | dced341b2d4f06668efaab33f88de5d287c0f45b (diff) | |
download | blackbird-op-linux-92fdd98cf8bdec4d6b0c510e2f073ac4fd059be8.tar.gz blackbird-op-linux-92fdd98cf8bdec4d6b0c510e2f073ac4fd059be8.zip |
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)
{
__free_page(buf->page);
}
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,
};
with
void generic_pipe_buf_get(struct pipe_inode_info *pipe, struct pipe_buffer *buf)
{
page_cache_get(buf->page);
}
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
get_page(page)
look at that page
__free_page(page)
look at that page
__free_page(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: Al Viro <viro@zeniv.linux.org.uk>
[ SDR - Removed no longer used tracing_pipe_buf_release ]
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'Documentation/driver-model')
0 files changed, 0 insertions, 0 deletions