Commit 54354c6a authored by Kees Cook's avatar Kees Cook Committed by Peter Zijlstra
Browse files

Revert "proc/wchan: use printk format instead of lookup_symbol_name()" 



This reverts commit 152c432b.

When a kernel address couldn't be symbolized for /proc/$pid/wchan, it
would leak the raw value, a potential information exposure. This is a
regression compared to the safer pre-v5.12 behavior.

Reported-by: default avatarkernel test robot <oliver.sang@intel.com>
Reported-by: default avatarVito Caputo <vcaputo@pengaru.com>
Reported-by: default avatarJann Horn <jannh@google.com>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20211008111626.090829198@infradead.org
parent 804bccba

fs/proc/base.c

+11 −8
Original line number Diff line number Diff line
@@ -67,6 +67,7 @@ 
#include <linux/mm.h>

#include <linux/swap.h>

#include <linux/rcupdate.h>

#include <linux/kallsyms.h>

#include <linux/stacktrace.h>

#include <linux/resource.h>

#include <linux/module.h>
@@ -386,17 +387,19 @@ static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns, 
			  struct pid *pid, struct task_struct *task)

{

	unsigned long wchan;

	char symname[KSYM_NAME_LEN];



	if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))

		goto print0;



	if (ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))

	wchan = get_wchan(task);

	else

		wchan = 0;

	if (wchan && !lookup_symbol_name(wchan, symname)) {

		seq_puts(m, symname);

		return 0;

	}



	if (wchan)

		seq_printf(m, "%ps", (void *) wchan);

	else

print0:

	seq_putc(m, '0');



	return 0;

}

#endif /* CONFIG_KALLSYMS */