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

Liam Howlett
2021-04-20T16:50:51Z

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@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;
--
2.30.2