| Message ID | 1345620143-17289-3-git-send-email-mikey@neuling.org (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c index f3a82dd..768182c 100644 --- a/arch/powerpc/kernel/hw_breakpoint.c +++ b/arch/powerpc/kernel/hw_breakpoint.c @@ -253,7 +253,8 @@ int __kprobes hw_breakpoint_handler(struct die_args *args) /* Do not emulate user-space instructions, instead single-step them */ if (user_mode(regs)) { - bp->ctx->task->thread.last_hit_ubp = bp; + if (bp->ctx->task) + bp->ctx->task->thread.last_hit_ubp = bp; regs->msr |= MSR_SE; goto out; }
Currently if you are doing a global perf recording with hardware breakpoints (ie perf record -e mem:0xdeadbeef -a), you can oops with: Faulting instruction address: 0xc000000000738890 cpu 0xc: Vector: 300 (Data Access) at [c0000003f76af8d0] pc: c000000000738890: .hw_breakpoint_handler+0xa0/0x1e0 lr: c000000000738830: .hw_breakpoint_handler+0x40/0x1e0 sp: c0000003f76afb50 msr: 8000000000001032 dar: 6f0 dsisr: 42000000 current = 0xc0000003f765ac00 paca = 0xc00000000f262a00 softe: 0 irq_happened: 0x01 pid = 6810, comm = loop-read enter ? for help [c0000003f76afbe0] c00000000073cd04 .notifier_call_chain.isra.0+0x84/0xe0 [c0000003f76afc80] c00000000073cdbc .notify_die+0x3c/0x60 [c0000003f76afd20] c0000000000139f0 .do_dabr+0x40/0xf0 [c0000003f76afe30] c000000000005a9c handle_dabr_fault+0x14/0x48 --- Exception: 300 (Data Access) at 0000000010000480 SP (ff8679e0) is in userspace This is because we don't check to see if the break point is associated with task before we deference the task_struct pointer. This checks pointer before dereferencing it. Signed-off-by: Michael Neuling <mikey@neuling.org> --- arch/powerpc/kernel/hw_breakpoint.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)