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| author | Deepanshu Kartikey <kartikey406@gmail.com> | 2026-08-17 19:36:55 +0530 |
|---|---|---|
| committer | Steven Rostedt <rostedt@goodmis.org> | 2026-08-22 17:43:42 -0400 |
| commit | 372f8534244d632ad5118e8a87a11291b01712d3 (patch) | |
| tree | f451751231e8cada28d31c1d01bd63feb5ee6843 /kernel | |
| parent | 649bc7df3e5d7be6f7996a95084037dbf3cad1e5 (diff) | |
| download | linux-next-372f8534244d632ad5118e8a87a11291b01712d3.tar.gz linux-next-372f8534244d632ad5118e8a87a11291b01712d3.zip | |
tracing: Fix use-after-free in trace_pipe read on sub-buffer order change
Writing to buffer_subbuf_size_kb calls ring_buffer_subbuf_order_set(),
which frees every sub-buffer of the ring buffer, including the reader
page, and replaces them with newly allocated ones.
Readers of trace_pipe hold pointers into those pages. ring_buffer_peek()
looks up an event under cpu_buffer->reader_lock but returns the event
pointer after dropping the lock, and peek_next_entry() then calls
ring_buffer_event_length() and ring_buffer_event_data() on it. If the
sub-buffer order is changed in that window, the reader dereferences
freed memory:
BUG: KASAN: use-after-free in ring_buffer_peek+0x3e0/0x430
Read of size 1 at addr ffff88802a4cf010 by task syz-executor989/6002
Freed by:
free_buffer_page kernel/trace/ring_buffer.c:398 [inline]
ring_buffer_subbuf_order_set+0x1325/0x18e0 kernel/trace/ring_buffer.c:7444
buffer_subbuf_size_write+0x182/0x280 kernel/trace/trace.c:8221
Take trace_access_lock(RING_BUFFER_ALL_CPUS) around the order change.
This is the lock trace_pipe readers already hold across their entire
peek-and-print loop, so the swap can no longer race with a reader that
is dereferencing a peeked event.
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260817140655.5694-1-kartikey406@gmail.com
Fixes: f9b94daa542a ("ring-buffer: Set new size of the ring buffer sub page")
Reported-by: syzbot+685955db58555575fdd2@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=685955db58555575fdd2
Tested-by: syzbot+685955db58555575fdd2@syzkaller.appspotmail.com
Reviewed-by: Bradley Morgan <include@grrlz.net>
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel')
| -rw-r--r-- | kernel/trace/trace.c | 3 |
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 740c5f358b75..60c87977f1e3 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -8214,6 +8214,8 @@ buffer_subbuf_size_write(struct file *filp, const char __user *ubuf, /* Do not allow tracing while changing the order of the ring buffer */ tracing_stop_tr(tr); + trace_access_lock(RING_BUFFER_ALL_CPUS); + old_order = ring_buffer_subbuf_order_get(tr->array_buffer.buffer); if (old_order == order) goto out; @@ -8253,6 +8255,7 @@ buffer_subbuf_size_write(struct file *filp, const char __user *ubuf, #endif (*ppos)++; out: + trace_access_unlock(RING_BUFFER_ALL_CPUS); if (ret) cnt = ret; tracing_start_tr(tr); |