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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>
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Since commit e645535a954a ("tracing: Add option to use memmapped
memory for trace boot instance") changed trace_array_get_by_name() to
trace_array_create_systems(), enable_instances() does not reuse the
same name instance. Therefore, if an administrator mistakenly specifies
multiple `trace_instance=` options with duplicate names, all are
created but only the first is accessible via tracefs.
Check whether an instance with the same name already exists before
creating a new one, and reject duplicates with a warning.
Link: https://patch.msgid.link/178847790399.283263.5313150997200138426.stgit@devnote2
Fixes: e645535a954a ("tracing: Add option to use memmapped memory for trace boot instance")
Signed-off-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Sashiko reported that the code was using meta->nr_subbufs without making
sure that it matched the nr_pages + 1 on data that was assuming the two
were the same.
Add a check to the persistent ring buffer validation code to make sure
that the saved nr_subbufs matches what we expect.
Link: https://patch.msgid.link/20260903132728.7fb27d34@gandalf.local.home
Fixes: f5b95f1fa2ef3 ("ring-buffer: Validate the persistent meta data subbuf array")
Reported-by: sashiko-bot@kernel.org
Closes: https://lore.kernel.org/all/20260901164836.D962D1F000E9@smtp.kernel.org/
Reviewed-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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ring_buffer_read_page() rejects splice (full=1) reads on static buffers
(that is user-mapped, persistent or remote) because !read check assumes
unread pages must be swapped. However for those buffers we have no other
choice than memcpy the data.
For the memcpy case, only return an error when the writer is still on
the reader page for the splice interface to wait.
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260901155445.1475405-2-vdonnefort@google.com
Fixes: 117c39200d9d ("ring-buffer: Introducing ring-buffer mapping functions")
Signed-off-by: Vincent Donnefort <vdonnefort@google.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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The options files do not take the trace_array reference for the options
they represent. This could cause a use-after-free kernel crash if one of
these files is opened by one task and another task removes the instance
that the option is for. Because it doesn't take a reference upon opening,
it will not stop the removal which will free the options descriptor that
is being used.
As the options are somewhat dynamic in their creation at boot up, each
file represents a flag in the trace_array. The trace_array has an array of
indexes to represent each of these flags that is stored in the
trace_flags_index array. The address of the index array element is used to
pass to the inode->i_private pointer. Then that element is read which
holds the index (which represents the flag) and then the index is used to
calculate the trace_array descriptor from its trace_flags_index array.
One issue is that the index element can not be referenced until the
trace_array's reference is taken. To handle this, create a new helper
function called: trace_array_options_get() that will iterate all the
existing trace_arrays in the ftrace_trace_arrays list (under the
trace_types_lock), and compare the passed in address of the index element
with the entire array of the trace_array's trace_flags_index array.
If it matches, then up the corresponding trace_array's reference and
return.
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902121918.5a9e9d1b@gandalf.local.home
Fixes: 577b785f55168 ("tracing: add tracer dependent options to options directory")
Reported-by: sashiko-bot@kernel.org
Closes: https://lore.kernel.org/linux-trace-kernel/20260828135858.2AC501F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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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>
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