[124/181] mm: kasan: do not panic if both panic_on_warn and kasan_multishot set

Commit Message

Andrew Morton Oct. 13, 2020, 11:55 p.m. UTC

From: David Gow <[e-mail]>
Subject: mm: kasan: do not panic if both panic_on_warn and kasan_multishot set

KASAN errors will currently trigger a panic when panic_on_warn is set. 
This renders kasan_multishot useless, as further KASAN errors won't be
reported if the kernel has already paniced.  By making kasan_multishot
disable this behaviour for KASAN errors, we can still have the benefits of
panic_on_warn for non-KASAN warnings, yet be able to use kasan_multishot.

This is particularly important when running KASAN tests, which need to
trigger multiple KASAN errors: previously these would panic the system if
panic_on_warn was set, now they can run (and will panic the system should
non-KASAN warnings show up).

Link: https://lkml.kernel.org/r/[e-mail]
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: David Gow <[e-mail]>
Reviewed-by: Andrey Konovalov <[e-mail]>
Reviewed-by: Brendan Higgins <[e-mail]>
Tested-by: Andrey Konovalov <[e-mail]>
Cc: Andrey Ryabinin <[e-mail]>
Cc: Dmitry Vyukov <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Juri Lelli <[e-mail]>
Cc: Patricia Alfonso <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Shuah Khan <[e-mail]>
Cc: Vincent Guittot <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
---

 mm/kasan/report.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch

--- a/mm/kasan/report.c~mm-kasan-do-not-panic-if-both-panic_on_warn-and-kasan_multishot-set
+++ a/mm/kasan/report.c
@@ -95,7 +95,7 @@  static void end_report(unsigned long *fl
 	pr_err("==================================================================\n");
 	add_taint(TAINT_BAD_PAGE, LOCKDEP_NOW_UNRELIABLE);
 	spin_unlock_irqrestore(&report_lock, *flags);
-	if (panic_on_warn) {
+	if (panic_on_warn && !test_bit(KASAN_BIT_MULTI_SHOT, &kasan_flags)) {
 		/*
 		 * This thread may hit another WARN() in the panic path.
 		 * Resetting this prevents additional WARN() from panicking the