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    SubjectRe: [PATCH 3/3] arch/arm64/kernel/traps: Use find_vma_intersection() in traps for setting si_code
    On Tue, Apr 20, 2021 at 04:50:13PM +0000, Liam Howlett wrote:
    > 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;

    I'm not seeing how this addresses VM_GROWSDOWN as Catalin mentioned before.

    Will

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