From: Catalin Marinas <catalin.marinas@arm.com>
To: Liam Howlett <liam.howlett@oracle.com>
Cc: 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>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Amit Daniel Kachhap <amit.kachhap@arm.com>
Subject: Re: [PATCH] arch/arm64/kernel/traps: Use find_vma_intersection() in traps for setting si_code
Date: Mon, 12 Apr 2021 18:43:44 +0100 [thread overview]
Message-ID: <20210412174343.GG2060@arm.com> (raw)
In-Reply-To: <20210407150940.542103-1-Liam.Howlett@Oracle.com>
On Wed, Apr 07, 2021 at 03:11:06PM +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.
>
> 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 don't think your change is entirely correct either. We can have a
fault below the vma of a stack (with VM_GROWSDOWN) and
find_vma_intersection() would return NULL but it should be a SEGV_ACCERR
instead.
Maybe this should employ similar checks as __do_page_fault() (with
expand_stack() and VM_GROWSDOWN).
--
Catalin
next prev parent reply other threads:[~2021-04-12 17:43 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-04-07 15:11 [PATCH] arch/arm64/kernel/traps: Use find_vma_intersection() in traps for setting si_code Liam Howlett
2021-04-12 17:43 ` Catalin Marinas [this message]
2021-04-13 16:52 ` Liam Howlett
2021-04-13 18:00 ` Catalin Marinas
2021-04-14 16:30 ` Liam Howlett
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