Message ID | 20231210221250.7b9cc83c@rorschach.local.home |
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State | New |
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Series |
ring-buffer: Fix memory leak of free page
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Commit Message
Steven Rostedt
Dec. 11, 2023, 3:12 a.m. UTC
From: "Steven Rostedt (Google)" <rostedt@goodmis.org> Reading the ring buffer does a swap of a sub-buffer within the ring buffer with a empty sub-buffer. This allows the reader to have full access to the content of the sub-buffer that was swapped out without having to worry about contention with the writer. The readers call ring_buffer_alloc_read_page() to allocate a page that will be used to swap with the ring buffer. When the code is finished with the reader page, it calls ring_buffer_free_read_page(). Instead of freeing the page, it stores it as a spare. Then next call to ring_buffer_alloc_read_page() will return this spare instead of calling into the memory management system to allocate a new page. Unfortunately, on freeing of the ring buffer, this spare page is not freed, and causes a memory leak. Cc: stable@vger.kernel.org Fixes: 73a757e63114d ("ring-buffer: Return reader page back into existing ring buffer") Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> --- kernel/trace/ring_buffer.c | 2 ++ 1 file changed, 2 insertions(+)
Comments
On Sun, 10 Dec 2023 22:12:50 -0500 Steven Rostedt <rostedt@goodmis.org> wrote: > From: "Steven Rostedt (Google)" <rostedt@goodmis.org> > > Reading the ring buffer does a swap of a sub-buffer within the ring buffer > with a empty sub-buffer. This allows the reader to have full access to the > content of the sub-buffer that was swapped out without having to worry > about contention with the writer. > > The readers call ring_buffer_alloc_read_page() to allocate a page that > will be used to swap with the ring buffer. When the code is finished with > the reader page, it calls ring_buffer_free_read_page(). Instead of freeing > the page, it stores it as a spare. Then next call to > ring_buffer_alloc_read_page() will return this spare instead of calling > into the memory management system to allocate a new page. > > Unfortunately, on freeing of the ring buffer, this spare page is not > freed, and causes a memory leak. > Oops, Looks good to me. Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org> Thanks, > Cc: stable@vger.kernel.org > Fixes: 73a757e63114d ("ring-buffer: Return reader page back into existing ring buffer") > Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org> > --- > kernel/trace/ring_buffer.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > index a38e5a3c6803..dd37d21d6e55 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -1790,6 +1790,8 @@ static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) > free_buffer_page(bpage); > } > > + free_page((unsigned long)cpu_buffer->free_page); > + > kfree(cpu_buffer); > } > > -- > 2.42.0 >
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index a38e5a3c6803..dd37d21d6e55 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -1790,6 +1790,8 @@ static void rb_free_cpu_buffer(struct ring_buffer_per_cpu *cpu_buffer) free_buffer_page(bpage); } + free_page((unsigned long)cpu_buffer->free_page); + kfree(cpu_buffer); }