Re: [PATCH V2 09/10] kasan: Prevent deadlock in kasan reporting
From: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Date: 2015-08-27 12:08:17
Also in:
lkml
2015-08-26 11:26 GMT+03:00 Aneesh Kumar K.V [off-list ref]:
We we end up calling kasan_report in real mode, our shadow mapping for even spinlock variable will show poisoned.
Generally I agree with this patch. We should disable reports when we print report as early as possible to prevent recursion in case of bug in spinlock or printk etc. But I don't understand what is the problem that you observing. How we ended up with shadow poisoned for a valid spinlock struct? And since shadow poisoned for some valid memory we should get enormous amount of false positive reports.
quoted hunk ↗ jump to hunk
This will result in us calling kasan_report_error with lock_report spin lock held. To prevent this disable kasan reporting when we are priting error w.r.t kasan. Signed-off-by: Aneesh Kumar K.V <redacted> --- mm/kasan/report.c | 10 ++++++++++ 1 file changed, 10 insertions(+)diff --git a/mm/kasan/report.c b/mm/kasan/report.c index 79fbc5d14bd2..82b41eb83e43 100644 --- a/mm/kasan/report.c +++ b/mm/kasan/report.c@@ -185,6 +185,10 @@ void kasan_report_error(struct kasan_access_info *info) { unsigned long flags; + /* + * Make sure we don't end up in loop. + */ + kasan_disable_current(); spin_lock_irqsave(&report_lock, flags); pr_err("=================================" "=================================\n");@@ -194,12 +198,17 @@ void kasan_report_error(struct kasan_access_info *info) pr_err("=================================" "=================================\n"); spin_unlock_irqrestore(&report_lock, flags); + kasan_enable_current(); } void kasan_report_user_access(struct kasan_access_info *info) { unsigned long flags; + /* + * Make sure we don't end up in loop. + */ + kasan_disable_current(); spin_lock_irqsave(&report_lock, flags); pr_err("=================================" "=================================\n");@@ -212,6 +221,7 @@ void kasan_report_user_access(struct kasan_access_info *info) pr_err("=================================" "=================================\n"); spin_unlock_irqrestore(&report_lock, flags); + kasan_enable_current(); } void kasan_report(unsigned long addr, size_t size, --2.5.0