From: Kees Cook keescook@chromium.org
commit 54354c6a9f7fd5572d2b9ec108117c4f376d4d23 upstream.
This reverts commit 152c432b128cb043fc107e8f211195fe94b2159c.
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 Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/proc/base.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-)
--- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -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_fil 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 (wchan) - seq_printf(m, "%ps", (void *) wchan); - else - seq_putc(m, '0'); + if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)) + goto print0;
+ 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 */