| Message ID | 20220920200037.6727-1-palmer@rivosinc.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | f2913d006fcdb61719635e093d1b5dd0dafecac7 |
| Delegated to: | Palmer Dabbelt |
| Headers | show |
| Series | RISC-V: Avoid dereferening NULL regs in die() | expand |
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
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,
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);
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(-)