| 1 | From 4c1396cb576c9b14425558b73de1584c7a9735d7 Mon Sep 17 00:00:00 2001 |
| 2 | From: P J P <ppandit@redhat.com> |
| 3 | Date: Fri, 18 Dec 2015 11:35:07 +0530 |
| 4 | Subject: [PATCH] i386: avoid null pointer dereference |
| 5 | |
| 6 | Hello, |
| 7 | |
| 8 | A null pointer dereference issue was reported by Mr Ling Liu, CC'd here. It |
| 9 | occurs while doing I/O port write operations via hmp interface. In that, |
| 10 | 'current_cpu' remains null as it is not called from cpu_exec loop, which |
| 11 | results in the said issue. |
| 12 | |
| 13 | Below is a proposed (tested)patch to fix this issue; Does it look okay? |
| 14 | |
| 15 | === |
| 16 | From ae88a4947fab9a148cd794f8ad2d812e7f5a1d0f Mon Sep 17 00:00:00 2001 |
| 17 | From: Prasad J Pandit <pjp@fedoraproject.org> |
| 18 | Date: Fri, 18 Dec 2015 11:16:07 +0530 |
| 19 | Subject: [PATCH] i386: avoid null pointer dereference |
| 20 | |
| 21 | When I/O port write operation is called from hmp interface, |
| 22 | 'current_cpu' remains null, as it is not called from cpu_exec() |
| 23 | loop. This leads to a null pointer dereference in vapic_write |
| 24 | routine. Add check to avoid it. |
| 25 | |
| 26 | Reported-by: Ling Liu <liuling-it@360.cn> |
| 27 | Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org> |
| 28 | Message-Id: <alpine.LFD.2.20.1512181129320.9805@wniryva> |
| 29 | Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> |
| 30 | Signed-off-by: P J P <ppandit@redhat.com> |
| 31 | --- |
| 32 | hw/i386/kvmvapic.c | 15 ++++++++++----- |
| 33 | 1 file changed, 10 insertions(+), 5 deletions(-) |
| 34 | |
| 35 | diff --git a/hw/i386/kvmvapic.c b/hw/i386/kvmvapic.c |
| 36 | index c6d34b2..f0922da 100644 |
| 37 | --- a/hw/i386/kvmvapic.c |
| 38 | +++ b/hw/i386/kvmvapic.c |
| 39 | @@ -634,13 +634,18 @@ static int vapic_prepare(VAPICROMState *s) |
| 40 | static void vapic_write(void *opaque, hwaddr addr, uint64_t data, |
| 41 | unsigned int size) |
| 42 | { |
| 43 | - CPUState *cs = current_cpu; |
| 44 | - X86CPU *cpu = X86_CPU(cs); |
| 45 | - CPUX86State *env = &cpu->env; |
| 46 | - hwaddr rom_paddr; |
| 47 | VAPICROMState *s = opaque; |
| 48 | + X86CPU *cpu; |
| 49 | + CPUX86State *env; |
| 50 | + hwaddr rom_paddr; |
| 51 | |
| 52 | - cpu_synchronize_state(cs); |
| 53 | + if (!current_cpu) { |
| 54 | + return; |
| 55 | + } |
| 56 | + |
| 57 | + cpu_synchronize_state(current_cpu); |
| 58 | + cpu = X86_CPU(current_cpu); |
| 59 | + env = &cpu->env; |
| 60 | |
| 61 | /* |
| 62 | * The VAPIC supports two PIO-based hypercalls, both via port 0x7E. |
| 63 | -- |
| 64 | 2.6.3 |
| 65 | |