From: Conor Dooley <conor@kernel.org>
To: Palmer Dabbelt <palmer@rivosinc.com>
Cc: linux-riscv@lists.infradead.org,
kernel test robot <lkp@intel.com>,
Dan Carpenter <dan.carpenter@oracle.com>
Subject: Re: [PATCH] RISC-V: Avoid dereferening NULL regs in die()
Date: Tue, 20 Sep 2022 22:36:59 +0100 [thread overview]
Message-ID: <YyoyewwUNMMUgCru@spud> (raw)
In-Reply-To: <20220920200037.6727-1-palmer@rivosinc.com>
On Tue, Sep 20, 2022 at 01:00:37PM -0700, Palmer Dabbelt wrote:
> I don't think we can actually die() without a regs pointer, but the
> compiler was warning about a NULL check after a dereference. It seems
> prudent to just avoid the possibly-NULL dereference, given that when
> die()ing the system is already toast so who knows how we got there.
>
> Reported-by: kernel test robot <lkp@intel.com>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
I excitedly tried this in the hopes that I was actually hitting this
somehow with the crash-during-boot-with-no-splat that I am currently
bisecting, but sadly it was not the solution.
Either way it looks like a sane change so we at least can get something
out in an edge failure case.
> ---
> arch/riscv/kernel/traps.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/arch/riscv/kernel/traps.c b/arch/riscv/kernel/traps.c
> index 635e6ec26938..f3e96d60a2ff 100644
> --- a/arch/riscv/kernel/traps.c
> +++ b/arch/riscv/kernel/traps.c
> @@ -33,6 +33,7 @@ void die(struct pt_regs *regs, const char *str)
> {
> static int die_counter;
> int ret;
> + long cause;
>
> oops_enter();
>
> @@ -42,11 +43,13 @@ void die(struct pt_regs *regs, const char *str)
>
> pr_emerg("%s [#%d]\n", str, ++die_counter);
> print_modules();
> - show_regs(regs);
> + if (regs)
> + show_regs(regs);
>
> - ret = notify_die(DIE_OOPS, str, regs, 0, regs->cause, SIGSEGV);
> + cause = regs ? regs->cause : -1;
> + ret = notify_die(DIE_OOPS, str, regs, 0, cause, SIGSEGV);
>
> - if (regs && kexec_should_crash(current))
> + if (kexec_should_crash(current))
> crash_kexec(regs);
Had to go down the rabbit hole to see that there is an if(regs) around
the eventual user of this, so:
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
>
> bust_spinlocks(0);
> --
> 2.34.1
>
>
> _______________________________________________
> linux-riscv mailing list
> linux-riscv@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-riscv
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next prev parent reply other threads:[~2022-09-20 21:37 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-20 20:00 [PATCH] RISC-V: Avoid dereferening NULL regs in die() Palmer Dabbelt
2022-09-20 21:36 ` Conor Dooley [this message]
2022-10-13 5:15 ` Palmer Dabbelt
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