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

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This reverts commit 152c432b12.

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: kernel test robot <oliver.sang@intel.com>
Reported-by: Vito Caputo <vcaputo@pengaru.com>
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/20211008111626.090829198@infradead.org
This commit is contained in:
Kees Cook 2021-09-29 15:02:13 -07:00 committed by Peter Zijlstra
parent 804bccba71
commit 54354c6a9f
1 changed files with 11 additions and 8 deletions
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19
fs/proc/base.c
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@ -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))
wchan = get_wchan(task);
else
wchan = 0;
if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
goto print0;
if (wchan)
seq_printf(m, "%ps", (void *) wchan);
else
seq_putc(m, '0');
wchan = get_wchan(task);
if (wchan && !lookup_symbol_name(wchan, symname)) {
seq_puts(m, symname);
return 0;
}
print0:
seq_putc(m, '0');
return 0;
}
#endif /* CONFIG_KALLSYMS */