linux-kernel - [PATCH 3/3] arch/arm64/kernel/traps: Use find_vma_intersection() in traps for setting si

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Date:   Tue, 20 Apr 2021 16:50:13 +0000
From:   Liam Howlett <liam.howlett@...cle.com>
To:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Julien Grall <julien.grall@....com>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Liam Howlett <liam.howlett@...cle.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "bpf@...r.kernel.org" <bpf@...r.kernel.org>
Subject: [PATCH 3/3] arch/arm64/kernel/traps: Use find_vma_intersection() in
 traps for setting si_code

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.

Fixes: bd35a4adc413 (arm64: Port SWP/SWPB emulation support from arm)
Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.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;
-- 
2.30.2