* [PATCH] RISC-V: Avoid dereferening NULL regs in die()
@ 2022-09-20 20:00 Palmer Dabbelt
2022-09-20 21:36 ` Conor Dooley
2022-10-13 5:15 ` Palmer Dabbelt
0 siblings, 2 replies; 3+ messages in thread
From: Palmer Dabbelt @ 2022-09-20 20:00 UTC (permalink / raw)
To: linux-riscv; +Cc: Palmer Dabbelt, kernel test robot, Dan Carpenter
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>
---
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);
bust_spinlocks(0);
--
2.34.1
_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] RISC-V: Avoid dereferening NULL regs in die()
2022-09-20 20:00 [PATCH] RISC-V: Avoid dereferening NULL regs in die() Palmer Dabbelt
@ 2022-09-20 21:36 ` Conor Dooley
2022-10-13 5:15 ` Palmer Dabbelt
1 sibling, 0 replies; 3+ messages in thread
From: Conor Dooley @ 2022-09-20 21:36 UTC (permalink / raw)
To: Palmer Dabbelt; +Cc: linux-riscv, kernel test robot, Dan Carpenter
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
_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] RISC-V: Avoid dereferening NULL regs in die()
2022-09-20 20:00 [PATCH] RISC-V: Avoid dereferening NULL regs in die() Palmer Dabbelt
2022-09-20 21:36 ` Conor Dooley
@ 2022-10-13 5:15 ` Palmer Dabbelt
1 sibling, 0 replies; 3+ messages in thread
From: Palmer Dabbelt @ 2022-10-13 5:15 UTC (permalink / raw)
To: Palmer Dabbelt, linux-riscv; +Cc: Dan Carpenter, kernel test robot
On Tue, 20 Sep 2022 13:00:37 -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.
>
>
Applied, thanks!
[1/1] RISC-V: Avoid dereferening NULL regs in die()
https://git.kernel.org/palmer/c/f2913d006fcd
Best regards,
--
Palmer Dabbelt <palmer@rivosinc.com>
_______________________________________________
linux-riscv mailing list
linux-riscv@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-riscv
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2022-10-13 5:16 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-09-20 20:00 [PATCH] RISC-V: Avoid dereferening NULL regs in die() Palmer Dabbelt
2022-09-20 21:36 ` Conor Dooley
2022-10-13 5:15 ` Palmer Dabbelt
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).