| Message ID | e60a66f60c059237bbf5cec3623c162a1bb1cbcb.1640005703.git.renzhen.rz@alibaba-inc.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [v2] virtio_mem: fix panic on mb_states indexing overflow | expand |
Hi, 在 2021/12/20 22:15, David Hildenbrand 写道: > On 20.12.21 14:18, Eric Ren wrote: >> `mb_id` is unsigned integer, which is used to index >> `mb_states` array in reverse order. `mb_id` can decrease >> to `0UL - 1` that is a very large number, causing invalid >> address access. > Hi Eric, > > thanks for your report! > > The only way I can see this happening would be if > > next_mb_id == 0, in which case we would get > > _mb_id = _vm->sbm.next_mb_id - 1 > -> _mb_id = 0 - 1 = -1ULL In the for loop, eg. _vm->sbm.next_mb_id == 756 initial _mb_id = 755 _vm->sbm.first_mb_id == 0 _vm->sbm.mb_count[_state] == 1 _mb_id-- will decrease to 0, * at this time *, the condition below in loop is true: _mb_id >= _vm->sbm.first_mb_id && _vm->sbm.mb_count[_state]; in next iteration, _mb_id-- results in _mb_id == -1UL. -1UL > _vm->sbm.first_mb_id is true, then the condition is still true. There, we have a invalid mb_id number. > > Otherwise we should always stay above _vm->sbm.first_mb_id. > > Am I correct or am I missing something? > > > But in that case we would have to have > vm->sbm.first_mb_id == 0 > > and consequently the start address of the device would have to be at > address 0. > > ... but that does sound very weird, especially on x86_64? > > Do you have details about the device layout / position in guest physical > address space? Hope I've explained it clearly above :-) > > virtio_mem_bbm_for_each_bb_rev() would need a similar fix. Oh yes, thanks! Eric > > >> The calltrace is like below: >> ``` >> [ 286.344977] BUG: unable to handle page fault for address: ffffa95180cf8fff >> [ 286.345800] #PF: supervisor read access in kernel mode >> [ 286.346738] #PF: error_code(0x0000) - not-present page >> [ 286.347440] PGD 1000067 P4D 1000067 PUD 138c067 PMD 1840435067 PTE 0 >> [ 286.348156] Oops: 0000 [#1] SMP PTI [ 286.348556] CPU: 1 PID: 122 Comm: kworker/1:2 Tainted: G OE >> ... >> [ 286.350740] Workqueue: events_freezable virtio_mem_run_wq [virtio_mem] >> [ 286.351605] RIP: 0010:virtio_mem_unplug_request+0x418/0x890 [virtio_mem] >> [ 286.352519] Code: 0f 87 fc 00 00 00 4a 63 54 ac 30 48 83 bc d5 f8 00 00 00 00 48 89 d0 0f 8 >> 4 e5 00 00 00 48 8b b5 38 01 00 00 4c 89 e2 48 29 ca <0f> b6 34 16 39 c6 75 c7 40 80 fe 02 0f >> 82 a4 01 00 00 40 80 fe 03 >> [ 286.355030] RSP: 0018:ffffa95181c4bd50 EFLAGS: 00010286 >> [ 286.355737] RAX: 0000000000000005 RBX: 0000000000006100 RCX: 0000000000000000 >> [ 286.356752] RDX: ffffffffffffffff RSI: ffffa95180cf9000 RDI: ffff8e5dc393b348 >> [ 286.357649] RBP: ffff8e5dc393b200 R08: ffff8e463cd2b610 R09: 0000000000000021 >> [ 286.358627] R10: ffffa95181c4bcd0 R11: ffffa95181c4baa0 R12: ffffffffffffffff >> [ 286.359617] R13: 0000000000000003 R14: ffff8e5dc393b348 R15: 00000000fffffff0 >> [ 286.360503] FS: 0000000000000000(0000) GS:ffff8e463cd00000(0000) knlGS:0000000000000000 >> [ 286.361532] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 >> [ 286.362229] CR2: ffffa95180cf8fff CR3: 0000001846234000 CR4: 00000000000006e0 >> [ 286.363168] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 >> [ 286.364162] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 >> [ 286.365054] Call Trace: >> [ 286.365431] ? virtio_mem_run_wq+0x5a4/0x870 [virtio_mem] >> [ 286.366132] ? __schedule+0x4b3/0x800 >> [ 286.366547] ? process_one_work+0x18b/0x350 >> [ 286.367041] ? worker_thread+0x4f/0x3a0 >> [ 286.367675] ? rescuer_thread+0x350/0x350 >> [ 286.368234] ? kthread+0xfa/0x130 >> [ 286.368605] ? kthread_create_worker_on_cpu+0x70/0x70 >> [ 286.369155] ? ret_from_fork+0x1f/0x30 >> ``` >> >> Fixes by also checking its up boundary. >> >> Signed-off-by: Eric Ren <renzhengeek@gmail.com> >> -- >> v2: Correct the SOB >> Use _vm and remove duplicated spaces >> --- >> drivers/virtio/virtio_mem.c | 4 +++- >> 1 file changed, 3 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c >> index 96e5a8782769..f1ba0dadd47a 100644 >> --- a/drivers/virtio/virtio_mem.c >> +++ b/drivers/virtio/virtio_mem.c >> @@ -486,7 +486,9 @@ static int virtio_mem_sbm_mb_states_prepare_next_mb(struct virtio_mem *vm) >> >> #define virtio_mem_sbm_for_each_mb_rev(_vm, _mb_id, _state) \ >> for (_mb_id = _vm->sbm.next_mb_id - 1; \ >> - _mb_id >= _vm->sbm.first_mb_id && _vm->sbm.mb_count[_state]; \ >> + _mb_id >= _vm->sbm.first_mb_id && \ >> + _mb_id < _vm->sbm.next_mb_id && \ >> + _vm->sbm.mb_count[_state]; \ >> _mb_id--) \ >> if (virtio_mem_sbm_get_mb_state(_vm, _mb_id) == _state) >> >
Hi David, 在 12/21/21 9:53 PM, David Hildenbrand 写道: > Hi Eric, > >> _vm->sbm.first_mb_id == 0 > ^ that's precisely what I meant. Ah, finally got it! > > How could it *ever* be safe on x86-64 to let a virtio-mem device start > on physical address 0, eventually overlapping essentially all DMA, the > BIOS and the PCI hole. You're right! That clears my doubt why this "issue" can live so long there... util I see it. Yes, my setup is a very hacking enviroment. The device region start addr is wrongly assigned to 0! So, let's just drop this patch. Eric > > Thus my question: Is this a "fix" for x86-64 or is this a "prepare for" > for !x86-64 (e.g., arm64). > > If it's a fix, we want proper "Fixes:" and "Cc: stable" tags. But I > assume this is much rather a preparation for another architecture than > x86-64. > > Thanks! >
diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c index 96e5a8782769..f1ba0dadd47a 100644 --- a/drivers/virtio/virtio_mem.c +++ b/drivers/virtio/virtio_mem.c @@ -486,7 +486,9 @@ static int virtio_mem_sbm_mb_states_prepare_next_mb(struct virtio_mem *vm) #define virtio_mem_sbm_for_each_mb_rev(_vm, _mb_id, _state) \ for (_mb_id = _vm->sbm.next_mb_id - 1; \ - _mb_id >= _vm->sbm.first_mb_id && _vm->sbm.mb_count[_state]; \ + _mb_id >= _vm->sbm.first_mb_id && \ + _mb_id < _vm->sbm.next_mb_id && \ + _vm->sbm.mb_count[_state]; \ _mb_id--) \ if (virtio_mem_sbm_get_mb_state(_vm, _mb_id) == _state)
`mb_id` is unsigned integer, which is used to index `mb_states` array in reverse order. `mb_id` can decrease to `0UL - 1` that is a very large number, causing invalid address access. The calltrace is like below: ``` [ 286.344977] BUG: unable to handle page fault for address: ffffa95180cf8fff [ 286.345800] #PF: supervisor read access in kernel mode [ 286.346738] #PF: error_code(0x0000) - not-present page [ 286.347440] PGD 1000067 P4D 1000067 PUD 138c067 PMD 1840435067 PTE 0 [ 286.348156] Oops: 0000 [#1] SMP PTI [ 286.348556] CPU: 1 PID: 122 Comm: kworker/1:2 Tainted: G OE ... [ 286.350740] Workqueue: events_freezable virtio_mem_run_wq [virtio_mem] [ 286.351605] RIP: 0010:virtio_mem_unplug_request+0x418/0x890 [virtio_mem] [ 286.352519] Code: 0f 87 fc 00 00 00 4a 63 54 ac 30 48 83 bc d5 f8 00 00 00 00 48 89 d0 0f 8 4 e5 00 00 00 48 8b b5 38 01 00 00 4c 89 e2 48 29 ca <0f> b6 34 16 39 c6 75 c7 40 80 fe 02 0f 82 a4 01 00 00 40 80 fe 03 [ 286.355030] RSP: 0018:ffffa95181c4bd50 EFLAGS: 00010286 [ 286.355737] RAX: 0000000000000005 RBX: 0000000000006100 RCX: 0000000000000000 [ 286.356752] RDX: ffffffffffffffff RSI: ffffa95180cf9000 RDI: ffff8e5dc393b348 [ 286.357649] RBP: ffff8e5dc393b200 R08: ffff8e463cd2b610 R09: 0000000000000021 [ 286.358627] R10: ffffa95181c4bcd0 R11: ffffa95181c4baa0 R12: ffffffffffffffff [ 286.359617] R13: 0000000000000003 R14: ffff8e5dc393b348 R15: 00000000fffffff0 [ 286.360503] FS: 0000000000000000(0000) GS:ffff8e463cd00000(0000) knlGS:0000000000000000 [ 286.361532] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 286.362229] CR2: ffffa95180cf8fff CR3: 0000001846234000 CR4: 00000000000006e0 [ 286.363168] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 286.364162] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 286.365054] Call Trace: [ 286.365431] ? virtio_mem_run_wq+0x5a4/0x870 [virtio_mem] [ 286.366132] ? __schedule+0x4b3/0x800 [ 286.366547] ? process_one_work+0x18b/0x350 [ 286.367041] ? worker_thread+0x4f/0x3a0 [ 286.367675] ? rescuer_thread+0x350/0x350 [ 286.368234] ? kthread+0xfa/0x130 [ 286.368605] ? kthread_create_worker_on_cpu+0x70/0x70 [ 286.369155] ? ret_from_fork+0x1f/0x30 ``` Fixes by also checking its up boundary. Signed-off-by: Eric Ren <renzhengeek@gmail.com> -- v2: Correct the SOB Use _vm and remove duplicated spaces --- drivers/virtio/virtio_mem.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)