* [PATCH v2] powerpc/kprobes: Fix trap address when trap happened in real mode
@ 2020-02-18 14:29 Christophe Leroy
2020-02-18 14:55 ` Naveen N. Rao
0 siblings, 1 reply; 3+ messages in thread
From: Christophe Leroy @ 2020-02-18 14:29 UTC (permalink / raw)
To: Benjamin Herrenschmidt, Paul Mackerras, Michael Ellerman,
Larry Finger, Naveen N. Rao, Masami Hiramatsu
Cc: stable, linuxppc-dev, linux-kernel, Anil S Keshavamurthy,
David S. Miller
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 cleared, return 0 immediately.
Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
Fixes: 6cc89bad60a6 ("powerpc/kprobes: Invoke handlers directly")
Cc: stable@vger.kernel.org
Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
Cc: Masami Hiramatsu <mhiramat@kernel.org>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
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.leroy@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..673f349662e8 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))
+ return 0;
+
/*
* We don't want to be preempted for the entire
* duration of kprobe processing
--
2.25.0
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v2] powerpc/kprobes: Fix trap address when trap happened in real mode
2020-02-18 14:29 [PATCH v2] powerpc/kprobes: Fix trap address when trap happened in real mode Christophe Leroy
@ 2020-02-18 14:55 ` Naveen N. Rao
2020-02-18 19:37 ` Christophe Leroy
0 siblings, 1 reply; 3+ messages in thread
From: Naveen N. Rao @ 2020-02-18 14:55 UTC (permalink / raw)
To: Benjamin Herrenschmidt, Christophe Leroy, Larry Finger,
Masami Hiramatsu, Michael Ellerman, Paul Mackerras
Cc: stable, linuxppc-dev, David S. Miller, Anil S Keshavamurthy,
linux-kernel
Christophe Leroy 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 cleared, return 0 immediately.
>
> Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
> Fixes: 6cc89bad60a6 ("powerpc/kprobes: Invoke handlers directly")
> Cc: stable@vger.kernel.org
> Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> Cc: Masami Hiramatsu <mhiramat@kernel.org>
> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>
> ---
> 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.leroy@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..673f349662e8 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))
> + return 0;
> +
Should we also check for MSR_DR? Are there scenarios with ppc32 where
MSR_IR is on, but MSR_DR is off?
- Naveen
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v2] powerpc/kprobes: Fix trap address when trap happened in real mode
2020-02-18 14:55 ` Naveen N. Rao
@ 2020-02-18 19:37 ` Christophe Leroy
0 siblings, 0 replies; 3+ messages in thread
From: Christophe Leroy @ 2020-02-18 19:37 UTC (permalink / raw)
To: Naveen N. Rao, Benjamin Herrenschmidt, Larry Finger,
Masami Hiramatsu, Michael Ellerman, Paul Mackerras
Cc: stable, linuxppc-dev, David S. Miller, Anil S Keshavamurthy,
linux-kernel
Le 18/02/2020 à 15:55, Naveen N. Rao a écrit :
> Christophe Leroy 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 cleared, return 0 immediately.
>>
>> Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
>> Fixes: 6cc89bad60a6 ("powerpc/kprobes: Invoke handlers directly")
>> Cc: stable@vger.kernel.org
>> Cc: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
>> Cc: Masami Hiramatsu <mhiramat@kernel.org>
>> Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
>>
>> ---
>> 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.leroy@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..673f349662e8 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))
>> + return 0;
>> +
>
> Should we also check for MSR_DR? Are there scenarios with ppc32 where
> MSR_IR is on, but MSR_DR is off?
Yes indeed.
Christophe
^ permalink raw reply [flat|nested] 3+ messages in thread
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2020-02-18 14:29 [PATCH v2] powerpc/kprobes: Fix trap address when trap happened in real mode Christophe Leroy
2020-02-18 14:55 ` Naveen N. Rao
2020-02-18 19:37 ` Christophe Leroy
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