get_wchan() is racy by design, it may access volatile stack of running task, thus it may access redzone in a stack frame and cause KASAN to warn about this.
Use kasan_disable_current()/kasan_enable_current() to silence these warnings. Reported-by: Sasha Levin <[email protected]> Signed-off-by: Andrey Ryabinin <[email protected]> --- Perhaps it would be better to add something like this: READ_ONCE_NOCHECK() { kasan_disable_current(); READ_ONCE(); kasan_enable_current(); } ? arch/x86/kernel/process.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-) diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 39e585a..0488eb9 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -13,6 +13,7 @@ #include <linux/random.h> #include <linux/user-return-notifier.h> #include <linux/dmi.h> +#include <linux/kasan.h> #include <linux/utsname.h> #include <linux/stackprotector.h> #include <linux/tick.h> @@ -514,7 +515,7 @@ unsigned long arch_randomize_brk(struct mm_struct *mm) */ unsigned long get_wchan(struct task_struct *p) { - unsigned long start, bottom, top, sp, fp, ip; + unsigned long start, bottom, top, sp, fp, ip, ret = 0; int count = 0; if (!p || p == current || p->state == TASK_RUNNING) @@ -550,14 +551,21 @@ unsigned long get_wchan(struct task_struct *p) if (sp < bottom || sp > top) return 0; + kasan_disable_current(); fp = READ_ONCE(*(unsigned long *)sp); do { if (fp < bottom || fp > top) - return 0; + goto out; + ip = READ_ONCE(*(unsigned long *)(fp + sizeof(unsigned long))); - if (!in_sched_functions(ip)) - return ip; + if (!in_sched_functions(ip)) { + ret = ip; + goto out; + } fp = READ_ONCE(*(unsigned long *)fp); } while (count++ < 16 && p->state != TASK_RUNNING); - return 0; + +out: + kasan_enable_current(); + return ret; } -- 2.4.9 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
