[PATCH] arch/arm64/kernel/traps: Use find_vma_intersection() in traps for setting si_code

From: Liam Howlett <liam.howlett@oracle.com>
To: Catalin Marinas <catalin.marinas@arm.com>,
	Andre Przywara <andre.przywara@arm.com>,
	Will Deacon <will@kernel.org>,
	Peter Collingbourne <pcc@google.com>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	"bpf@vger.kernel.org" <bpf@vger.kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Andrii Nakryiko <andrii@kernel.org>,
	Amit Daniel Kachhap <amit.kachhap@arm.com>
Subject: [PATCH] arch/arm64/kernel/traps: Use find_vma_intersection() in traps for setting si_code
Date: Wed, 7 Apr 2021 15:11:06 +0000	[thread overview]
Message-ID: <20210407150940.542103-1-Liam.Howlett@Oracle.com> (raw)

find_vma() will continue to search upwards until the end of the virtual
memory space.  This means the si_code would almost never be set to
SEGV_MAPERR even when the address falls outside of any VMA.  The result
is that the si_code is not reliable as it may or may not be set to the
correct result, depending on where the address falls in the address
space.

Using find_vma_intersection() allows for what is intended by only
returning a VMA if it falls within the range provided, in this case a
window of 1.

Signed-off-by: Liam R. Howlett <Liam.Howlett@Oracle.com>
---
 arch/arm64/kernel/traps.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kernel/traps.c b/arch/arm64/kernel/traps.c
index a05d34f0e82a..a44007904a64 100644
--- a/arch/arm64/kernel/traps.c
+++ b/arch/arm64/kernel/traps.c
@@ -383,9 +383,10 @@ void force_signal_inject(int signal, int code, unsigned long address, unsigned i
 void arm64_notify_segfault(unsigned long addr)
 {
 	int code;
+	unsigned long ut_addr = untagged_addr(addr);
 
 	mmap_read_lock(current->mm);
-	if (find_vma(current->mm, untagged_addr(addr)) == NULL)
+	if (find_vma_intersection(current->mm, ut_addr, ut_addr + 1) == NULL)
 		code = SEGV_MAPERR;
 	else
 		code = SEGV_ACCERR;
-- 
2.30.0
