linux-kernel - [PATCH] MIPS: Fix strnlen

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Date:   Thu, 15 Apr 2021 23:26:40 +0200
From:   Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To:     linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] MIPS: Fix strnlen_user access check

Commit 04324f44cb69 ("MIPS: Remove get_fs/set_fs") changed the access_ok
for strnlen_user to check the whole range, which broke some callers
of strndup_user(). Restore the old behaviour and just check the first byte.

Fixes: 04324f44cb69 ("MIPS: Remove get_fs/set_fs")
Signed-off-by: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
---
 arch/mips/include/asm/uaccess.h | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/mips/include/asm/uaccess.h b/arch/mips/include/asm/uaccess.h
index ab47e597656a..783fecce65c8 100644
--- a/arch/mips/include/asm/uaccess.h
+++ b/arch/mips/include/asm/uaccess.h
@@ -614,8 +614,8 @@ static inline long strnlen_user(const char __user *s, long n)
 {
 	long res;
 
-	if (!access_ok(s, n))
-		return -0;
+	if (!access_ok(s, 1))
+		return 0;
 
 	might_fault();
 	__asm__ __volatile__(
-- 
2.29.2