From: Christophe Leroy <christophe.leroy@xxxxxx>
commit 21f8b2fa3ca5b01f7a2b51b89ce97a3705a15aa0 upstream.
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) {
BUG: Unable to handle kernel data access on read at 0x0000e268
Faulting instruction address: 0xc000ec34
Oops: Kernel access of bad area, sig: 11 [#1]
BE PAGE_SIZE=16K PREEMPT CMPC885
Modules linked in:
CPU: 0 PID: 429 Comm: cat Not tainted 5.6.0-rc1-s3k-dev-00824-g84195dc6c58a #3267
NIP: c000ec34 LR: c000ecd8 CTR: c019cab8
REGS: ca4d3b58 TRAP: 0300 Not tainted (5.6.0-rc1-s3k-dev-00824-g84195dc6c58a)
MSR: 00001032 <ME,IR,DR,RI> CR: 2a4d3c52 XER: 00000000
DAR: 0000e268 DSISR: c0000000
GPR00: c000b09c ca4d3c10 c66d0620 00000000 ca4d3c60 00000000 00009032 00000000
GPR08: 00020000 00000000 c087de44 c000afe0 c66d0ad0 100d3dd6 fffffff3 00000000
GPR16: 00000000 00000041 00000000 ca4d3d70 00000000 00000000 0000416d 00000000
GPR24: 00000004 c53b6128 00000000 0000e268 00000000 c07c0000 c07bb6fc ca4d3c60
NIP [c000ec34] kprobe_handler+0x128/0x290
LR [c000ecd8] kprobe_handler+0x1cc/0x290
Call Trace:
[ca4d3c30] [c000b09c] program_check_exception+0xbc/0x6fc
[ca4d3c50] [c000e43c] ret_from_except_full+0x0/0x4
--- interrupt: 700 at 0xe268
Instruction dump:
913e0008 81220000 38600001 3929ffff 91220000 80010024 bb410008 7c0803a6
38210020 4e800020 38600000 4e800020 <813b0000> 6d2a7fe0 2f8a0008 419e0154
---[ 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.
Reported-by: Larry Finger <Larry.Finger@xxxxxxxxxxxx>
Fixes: 6cc89bad60a6 ("powerpc/kprobes: Invoke handlers directly")
Cc: stable@xxxxxxxxxxxxxxx # v4.10+
Signed-off-by: Christophe Leroy <christophe.leroy@xxxxxx>
Reviewed-by: Masami Hiramatsu <mhiramat@xxxxxxxxxx>
Reviewed-by: Naveen N. Rao <naveen.n.rao@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Link: https://lore.kernel.org/r/424331e2006e7291a1bfe40e7f3fa58825f565e1.1582054578.git.christophe.leroy@xxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/powerpc/kernel/kprobes.c | 3 +++
1 file changed, 3 insertions(+)
--- 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
