The following commit has been merged into the sched/core branch of tip: Commit-ID: 54354c6a9f7fd5572d2b9ec108117c4f376d4d23 Gitweb: https://git.kernel.org/tip/54354c6a9f7fd5572d2b9ec108117c4f376d4d23 Author: Kees Cook <keescook@xxxxxxxxxxxx> AuthorDate: Wed, 29 Sep 2021 15:02:13 -07:00 Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx> CommitterDate: Fri, 15 Oct 2021 11:25:13 +02:00 Revert "proc/wchan: use printk format instead of lookup_symbol_name()" 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@xxxxxxxxx> Reported-by: Vito Caputo <vcaputo@xxxxxxxxxxx> Reported-by: Jann Horn <jannh@xxxxxxxxxx> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Link: https://lkml.kernel.org/r/20211008111626.090829198@xxxxxxxxxxxxx --- fs/proc/base.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index 533d583..1f39409 100644 --- 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_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 */
