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[ Upstream commit 1fdf938168c4d26fa279d4f204768690d1f9c4ae ]
Currently perf aborts when it finds an invalid command. I guess it
depends on the environment as I have some custom commands in the path.
$ perf bad-command
perf: 'bad-command' is not a perf-command. See 'perf --help'.
Aborted (core dumped)
It's because the exclude_cmds() in libsubcmd has a use-after-free when
it removes some entries. After copying one to another entry, it keeps
the pointer in the both position. And the next copy operation will free
the later one but it's the same entry in the previous one.
For example, let's say cmds = { A, B, C, D, E } and excludes = { B, E }.
ci cj ei cmds-name excludes
-----------+--------------------
0 0 0 | A B : cmp < 0, ci == cj
1 1 0 | B B : cmp == 0
2 1 1 | C E : cmp < 0, ci != cj
At this point, it frees cmds->names[1] and cmds->names[1] is assigned to
cmds->names[2].
3 2 1 | D E : cmp < 0, ci != cj
Now it frees cmds->names[2] but it's the same as cmds->names[1]. So
accessing cmds->names[1] will be invalid.
This makes the subcmd tests succeed.
$ perf test subcmd
69: libsubcmd help tests :
69.1: Load subcmd names : Ok
69.2: Uniquify subcmd names : Ok
69.3: Exclude duplicate subcmd names : Ok
Fixes: 4b96679170 ("libsubcmd: Avoid SEGV/use-after-free when commands aren't excluded")
Reviewed-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20250701201027.1171561-3-namhyung@kernel.org
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.