From 6d9c00c67b4768105e8ae3d213484095c744eea8 Mon Sep 17 00:00:00 2001 From: Michael Neuling Date: Wed, 22 Aug 2012 20:30:43 +0000 Subject: [PATCH] powerpc: Fix null pointer deref in perf hardware breakpoints 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 changes the update to use current. Signed-off-by: Michael Neuling Signed-off-by: Benjamin Herrenschmidt --- arch/powerpc/kernel/hw_breakpoint.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c index f3a82dde61db..956a4c496de9 100644 --- a/arch/powerpc/kernel/hw_breakpoint.c +++ b/arch/powerpc/kernel/hw_breakpoint.c @@ -253,7 +253,7 @@ 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; + current->thread.last_hit_ubp = bp; regs->msr |= MSR_SE; goto out; } -- 2.20.1