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kprobes: Skip clearing aggrprobe's post_handler in kprobe-on-ftrace case
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[ Upstream commit 5dd7caf ]

In __unregister_kprobe_top(), if the currently unregistered probe has
post_handler but other child probes of the aggrprobe do not have
post_handler, the post_handler of the aggrprobe is cleared. If this is
a ftrace-based probe, there is a problem. In later calls to
disarm_kprobe(), we will use kprobe_ftrace_ops because post_handler is
NULL. But we're armed with kprobe_ipmodify_ops. This triggers a WARN in
__disarm_kprobe_ftrace() and may even cause use-after-free:

  Failed to disarm kprobe-ftrace at kernel_clone+0x0/0x3c0 (error -2)
  WARNING: CPU: 5 PID: 137 at kernel/kprobes.c:1135 __disarm_kprobe_ftrace.isra.21+0xcf/0xe0
  Modules linked in: testKprobe_007(-)
  CPU: 5 PID: 137 Comm: rmmod Not tainted 6.1.0-rc4-dirty #18
  [...]
  Call Trace:
   <TASK>
   __disable_kprobe+0xcd/0xe0
   __unregister_kprobe_top+0x12/0x150
   ? mutex_lock+0xe/0x30
   unregister_kprobes.part.23+0x31/0xa0
   unregister_kprobe+0x32/0x40
   __x64_sys_delete_module+0x15e/0x260
   ? do_user_addr_fault+0x2cd/0x6b0
   do_syscall_64+0x3a/0x90
   entry_SYSCALL_64_after_hwframe+0x63/0xcd
   [...]

For the kprobe-on-ftrace case, we keep the post_handler setting to
identify this aggrprobe armed with kprobe_ipmodify_ops. This way we
can disarm it correctly.

Link: https://lore.kernel.org/all/[email protected]/

Fixes: 0bc11ed ("kprobes: Allow kprobes coexist with livepatch")
Reported-by: Zhao Gongyi <[email protected]>
Suggested-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Li Huafei <[email protected]>
Acked-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Masami Hiramatsu (Google) <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
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@gregkh
Li Huafei authored and gregkh committed Nov 25, 2022
1 parent 28f7ff5 commit 7b0007b
Showing 1 changed file with 7 additions and 1 deletion.
8 changes: 7 additions & 1 deletion kernel/kprobes.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1792,7 +1792,13 @@ static int __unregister_kprobe_top(struct kprobe *p)
if ((list_p != p) && (list_p->post_handler))
goto noclean;
}
ap->post_handler = NULL;
/*
* For the kprobe-on-ftrace case, we keep the
* post_handler setting to identify this aggrprobe
* armed with kprobe_ipmodify_ops.
*/
if (!kprobe_ftrace(ap))
ap->post_handler = NULL;
}
noclean:
/*
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