proc: check permissions earlier for /proc/*/wchan
get_wchan() accesses stack page before permissions are checked, let's
not play this game.
Link: http://lkml.kernel.org/r/20180217071923.GA16074@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/proc/base.c b/fs/proc/base.c
index d5324686..d8b5a16 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -388,14 +388,17 @@ static int proc_pid_wchan(struct seq_file *m, struct pid_namespace *ns,
unsigned long wchan;
char symname[KSYM_NAME_LEN];
+ if (!ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS))
+ goto print0;
+
wchan = get_wchan(task);
-
- if (wchan && ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS)
- && !lookup_symbol_name(wchan, symname))
+ if (wchan && !lookup_symbol_name(wchan, symname)) {
seq_printf(m, "%s", symname);
- else
- seq_putc(m, '0');
+ return 0;
+ }
+print0:
+ seq_putc(m, '0');
return 0;
}
#endif /* CONFIG_KALLSYMS */