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2026-09-04tracing: Fix subbuf resize races with trace_pipe_raw readersVincent Donnefort
Concurrent subbuffer resizes may crash trace_pipe_raw readers or leak uninitialized memory to userspace due to stale size values. Modify ring_buffer_alloc_read_page() to handle the resizing of an existing buffer_data_read_page if necessary and add a new ring_buffer_read_page_size(). This new function enables ring-buffer buffer_data_read_page users to not call the racy ring_buffer_subbuf_size_get(). This makes the spare_size member of ftrace_buffer_info redundant. Finally, handle buffer_data_read_page/reader_page order discrepancy in ring_buffer_read_page(). On a mismatch simply copy manually the data to the buffer_data_read_page. Link: https://lore.kernel.org/all/20260817140812.2C7D41F00A3A@smtp.kernel.org/ Link: https://patch.msgid.link/20260904164450.1345852-3-vdonnefort@google.com Fixes: bce761d75745 ("ring-buffer: Read and write to ring buffers with custom sub buffer size") Signed-off-by: Vincent Donnefort <vdonnefort@google.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2026-09-02ftrace: Synchronize the initialization of ftrace_opsgraftedSteven Rostedt
There's some internal state that ftrace_ops needs to have set, but since it can be declared outside of the ftrace.c code, it calls ftrace_ops_init() on the ops in every global function. The issue is that if two tasks call it on the same ops at the same time it is possible to have the initialization of one corrupt the initialization of the other call. Create a ops_mutex to use to synchronize every initialization of the ftrace_ops. The mutex is taken within checking the ftrace_ops flag that states it was initializied but the flag is checked again after the mutex has been taken. Checking first outside the mutex allows it to shortcut having to take the mutex. But then the check needs to be done again after the mute is taken in case of races. Cc: stable@vger.kernel.org Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock") Reported-by: sashiko-bot@kernel.org Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/ Signed-off-by: Steven Rostedt <rostedt@goodmis.org>