linux-kernel - [PATCH V2 3/4] mm/kasan: Don't use kasan shadow pointer in generic functions

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Message-Id: <1441614519-20298-3-git-send-email-aneesh.kumar@linux.vnet.ibm.com>
Date:	Mon,  7 Sep 2015 13:58:38 +0530
From:	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
To:	akpm@...ux-foundation.org, ryabinin.a.a@...il.com
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>
Subject: [PATCH V2 3/4] mm/kasan: Don't use kasan shadow pointer in generic functions

We can't use generic functions like print_hex_dump to access kasan
shadow region. This require us to setup another kasan shadow region
for the address passed (kasan shadow address). Some architectures won't
be able to do that. Hence make a copy of the shadow region row and
pass that to generic functions.

Reviewed-by: Andrey Ryabinin <ryabinin.a.a@...il.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@...ux.vnet.ibm.com>
---
 mm/kasan/report.c | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/mm/kasan/report.c b/mm/kasan/report.c
index d269f2087faf..c5367089703c 100644
--- a/mm/kasan/report.c
+++ b/mm/kasan/report.c
@@ -164,14 +164,20 @@ static void print_shadow_for_address(const void *addr)
 	for (i = -SHADOW_ROWS_AROUND_ADDR; i <= SHADOW_ROWS_AROUND_ADDR; i++) {
 		const void *kaddr = kasan_shadow_to_mem(shadow_row);
 		char buffer[4 + (BITS_PER_LONG/8)*2];
+		char shadow_buf[SHADOW_BYTES_PER_ROW];
 
 		snprintf(buffer, sizeof(buffer),
 			(i == 0) ? ">%p: " : " %p: ", kaddr);
-
+		/*
+		 * We should not pass a shadow pointer to generic
+		 * 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_row, SHADOW_BYTES_PER_ROW, 0);
+			shadow_buf, SHADOW_BYTES_PER_ROW, 0);
 		kasan_enable_current();
 
 		if (row_is_guilty(shadow_row, shadow))
-- 
2.5.0

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