mm/kasan: prevent deadlock in kasan reporting

When we end up calling kasan_report in real mode, our shadow mapping for
the spinlock variable will show poisoned.  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 <aneesh.kumar@linux.vnet.ibm.com>
Reviewed-by: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index c536708..7833f07 100644 (file)
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -173,12 +173,10 @@ static void print_shadow_for_address(const void *addr)
                 * function, because generic functions may try to
                 * access kasan mapping for the passed address.
                 */
-               kasan_disable_current();
                memcpy(shadow_buf, shadow_row, SHADOW_BYTES_PER_ROW);
                print_hex_dump(KERN_ERR, buffer,
                        DUMP_PREFIX_NONE, SHADOW_BYTES_PER_ROW, 1,
                        shadow_buf, SHADOW_BYTES_PER_ROW, 0);
-               kasan_enable_current();
 
                if (row_is_guilty(shadow_row, shadow))
                        pr_err("%*c\n",
@@ -195,6 +193,10 @@ 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");
@@ -204,12 +206,17 @@ 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");
@@ -222,6 +229,7 @@ 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,