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ftrace: use preempt_enable/disable notrace macros to avoid double fault

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Since the backport commit eea46baf14 ("ftrace: Fix possible
use-after-free issue in ftrace_location()") on linux-5.4.y branch, the
old ftrace_int3_handler()->ftrace_location() path has included
rcu_read_lock(), which has mcount location inside and leads to potential
double fault.

Replace rcu_read_lock/unlock with preempt_enable/disable notrace macros
so that the mcount location does not appear on the int3 handler path.

This fix is specific to linux-5.4.y branch, the only branch still using
ftrace_int3_handler with commit e60b613df8b6 ("ftrace: Fix possible
use-after-free issue in ftrace_location()") backported. It also avoids
the need to backport the code conversion to text_poke() on this branch.

Reported-by: Koichiro Den <koichiro.den@canonical.com>
Closes: https://lore.kernel.org/all/74gjhwxupvozwop7ndhrh7t5qeckomt7yqvkkbm5j2tlx6dkfk@rgv7sijvry2k
Fixes: eea46baf14 ("ftrace: Fix possible use-after-free issue in ftrace_location()") # linux-5.4.y
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
Signed-off-by: Koichiro Den <koichiro.den@canonical.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Koichiro Den 2025-01-08 12:17:36 +09:00 • committed by Greg Kroah-Hartman
parent 66cd37660e
commit 177516053e
1 changed files with 2 additions and 2 deletions
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4
kernel/trace/ftrace.c
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@ -1554,7 +1554,7 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end)
struct dyn_ftrace key;
unsigned long ip = 0;
rcu_read_lock();
preempt_disable_notrace();
key.ip = start;
key.flags = end; /* overload flags, as it is unsigned long */
@ -1572,7 +1572,7 @@ unsigned long ftrace_location_range(unsigned long start, unsigned long end)
break;
}
}
rcu_read_unlock();
preempt_enable_notrace();
return ip;
}