On Tue, Apr 17, 2018 at 1:03 PM, Kees Cook <keescook@xxxxxxxxxxxx> wrote: > The above bfq_dispatch_request+0x99/0xad0 is still > __bfq_dispatch_request at block/bfq-iosched.c:3902, just with KASAN > removed. 0x99 is 153 decimal: > > (gdb) disass bfq_dispatch_request > Dump of assembler code for function bfq_dispatch_request: > ... > 0xffffffff8134b2ad <+141>: test %rax,%rax > 0xffffffff8134b2b0 <+144>: je 0xffffffff8134b2bd > <bfq_dispatch_request+157> > 0xffffffff8134b2b2 <+146>: addl $0x1,0x100(%rax) > 0xffffffff8134b2b9 <+153>: addl $0x1,0x3c(%rbx) > 0xffffffff8134b2bd <+157>: orl $0x2,0x18(%r12) > 0xffffffff8134b2c3 <+163>: test %ebp,%ebp > 0xffffffff8134b2c5 <+165>: je 0xffffffff8134b2ce > <bfq_dispatch_request+174> > 0xffffffff8134b2c7 <+167>: mov 0x108(%r14),%rax > 0xffffffff8134b2ce <+174>: mov %r15,%rdi > 0xffffffff8134b2d1 <+177>: callq 0xffffffff81706f90 <_raw_spin_unlock_irq> > > Just as a sanity-check, at +157 %r12 should be rq, rq_flags is 0x18 > offset from, $0x2 is RQF_STARTED, so that maps to "rq->rq_flags |= > RQF_STARTED", the next C statement. I don't know what +146 is, though? > An increment of something 256 bytes offset? There's a lot of inline > fun and reordering happening here, so I'm ignoring that for the > moment. No -- I'm reading this wrong. The RIP is the IP _after_ the trap, so +146 is the offender. [ 29.284746] watchpoint @ ffff95d41a0fe580 triggered [ 29.285349] sense before:ffff95d41f45f700 after:ffff95d41f45f701 (@ffff95d41a 0fe580) [ 29.286176] elevator before:ffff95d419419c00 after:ffff95d419419c00 [ 29.286847] elevator_data before:ffff95d419418c00 after:ffff95d419418c00 ... [ 29.295069] RIP: 0010:bfq_dispatch_request+0x99/0xbb0 [ 29.295622] RSP: 0018:ffffb26e01707a40 EFLAGS: 00000002 [ 29.296181] RAX: ffff95d41a0fe480 RBX: ffff95d419418c00 RCX: ffff95d419418c08 RAX is ffff95d41a0fe480 and sense is stored at ffff95d41a0fe580, exactly 0x100 away. WTF is this addl? -Kees -- Kees Cook Pixel Security
