On Tue, 18 Feb 2020 19:38:27 +0000 (UTC) Christophe Leroy <christophe.le...@c-s.fr> wrote:
> When a program check exception happens while MMU translation is > disabled, following Oops happens in kprobe_handler() in the following > code: > > } else if (*addr != BREAKPOINT_INSTRUCTION) { > > [ 33.098554] BUG: Unable to handle kernel data access on read at 0x0000e268 > [ 33.105091] Faulting instruction address: 0xc000ec34 > [ 33.110010] Oops: Kernel access of bad area, sig: 11 [#1] > [ 33.115348] BE PAGE_SIZE=16K PREEMPT CMPC885 > [ 33.119540] Modules linked in: > [ 33.122591] CPU: 0 PID: 429 Comm: cat Not tainted > 5.6.0-rc1-s3k-dev-00824-g84195dc6c58a #3267 > [ 33.131005] NIP: c000ec34 LR: c000ecd8 CTR: c019cab8 > [ 33.136002] REGS: ca4d3b58 TRAP: 0300 Not tainted > (5.6.0-rc1-s3k-dev-00824-g84195dc6c58a) > [ 33.144324] MSR: 00001032 <ME,IR,DR,RI> CR: 2a4d3c52 XER: 00000000 > [ 33.150699] DAR: 0000e268 DSISR: c0000000 > [ 33.150699] GPR00: c000b09c ca4d3c10 c66d0620 00000000 ca4d3c60 00000000 > 00009032 00000000 > [ 33.150699] GPR08: 00020000 00000000 c087de44 c000afe0 c66d0ad0 100d3dd6 > fffffff3 00000000 > [ 33.150699] GPR16: 00000000 00000041 00000000 ca4d3d70 00000000 00000000 > 0000416d 00000000 > [ 33.150699] GPR24: 00000004 c53b6128 00000000 0000e268 00000000 c07c0000 > c07bb6fc ca4d3c60 > [ 33.188015] NIP [c000ec34] kprobe_handler+0x128/0x290 > [ 33.192989] LR [c000ecd8] kprobe_handler+0x1cc/0x290 > [ 33.197854] Call Trace: > [ 33.200340] [ca4d3c30] [c000b09c] program_check_exception+0xbc/0x6fc > [ 33.206590] [ca4d3c50] [c000e43c] ret_from_except_full+0x0/0x4 > [ 33.212392] --- interrupt: 700 at 0xe268 > [ 33.270401] Instruction dump: > [ 33.273335] 913e0008 81220000 38600001 3929ffff 91220000 80010024 bb410008 > 7c0803a6 > [ 33.280992] 38210020 4e800020 38600000 4e800020 <813b0000> 6d2a7fe0 > 2f8a0008 419e0154 > [ 33.288841] ---[ end trace 5b9152d4cdadd06d ]--- > > kprobe is not prepared to handle events in real mode and functions > running in real mode should have been blacklisted, so kprobe_handler() > can safely bail out telling 'this trap is not mine' for any trap that > happened while in real-mode. > > If the trap happened with MSR_IR or MSR_DR cleared, return 0 immediately. > Looks good to me. Reviewed-by: Masami Hiramatsu <mhira...@kernel.org> Thank you! > Reported-by: Larry Finger <larry.fin...@lwfinger.net> > Fixes: 6cc89bad60a6 ("powerpc/kprobes: Invoke handlers directly") > Cc: sta...@vger.kernel.org > Cc: Naveen N. Rao <naveen.n....@linux.vnet.ibm.com> > Cc: Masami Hiramatsu <mhira...@kernel.org> > Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr> > > --- > v3: Also bail out if MSR_DR is cleared. > > Resending v2 with a more appropriate name > > v2: bailing out instead of converting real-time address to virtual and > continuing. > > The bug might have existed even before that commit from Naveen. > > Signed-off-by: Christophe Leroy <christophe.le...@c-s.fr> > --- > arch/powerpc/kernel/kprobes.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/arch/powerpc/kernel/kprobes.c b/arch/powerpc/kernel/kprobes.c > index 2d27ec4feee4..9b340af02c38 100644 > --- a/arch/powerpc/kernel/kprobes.c > +++ b/arch/powerpc/kernel/kprobes.c > @@ -264,6 +264,9 @@ int kprobe_handler(struct pt_regs *regs) > if (user_mode(regs)) > return 0; > > + if (!(regs->msr & MSR_IR) || !(regs->msr & MSR_DR)) > + return 0; > + > /* > * We don't want to be preempted for the entire > * duration of kprobe processing > -- > 2.25.0 > -- Masami Hiramatsu <mhira...@kernel.org>