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author | Andrea Parri (Microsoft) <parri.andrea@gmail.com> | 2022-04-19 14:23:25 +0200 |
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committer | Wei Liu <wei.liu@kernel.org> | 2022-04-25 15:51:13 +0000 |
commit | a765ed47e45166451680ee9af2b9e435c82ec3ba (patch) | |
tree | b94a72b2a71bf59648595591c8b56887d2ae05c9 /net/vmw_vsock/hyperv_transport.c | |
parent | b91eaf7267cf7aec0a4e087decf7770dfb694d78 (diff) | |
download | linux-a765ed47e45166451680ee9af2b9e435c82ec3ba.tar.gz linux-a765ed47e45166451680ee9af2b9e435c82ec3ba.tar.bz2 linux-a765ed47e45166451680ee9af2b9e435c82ec3ba.zip |
PCI: hv: Fix synchronization between channel callback and hv_compose_msi_msg()
Dexuan wrote:
"[...] when we disable AccelNet, the host PCI VSP driver sends a
PCI_EJECT message first, and the channel callback may set
hpdev->state to hv_pcichild_ejecting on a different CPU. This can
cause hv_compose_msi_msg() to exit from the loop and 'return', and
the on-stack variable 'ctxt' is invalid. Now, if the response
message from the host arrives, the channel callback will try to
access the invalid 'ctxt' variable, and this may cause a crash."
Schematically:
Hyper-V sends PCI_EJECT msg
hv_pci_onchannelcallback()
state = hv_pcichild_ejecting
hv_compose_msi_msg()
alloc and init comp_pkt
state == hv_pcichild_ejecting
Hyper-V sends VM_PKT_COMP msg
hv_pci_onchannelcallback()
retrieve address of comp_pkt
'free' comp_pkt and return
comp_pkt->completion_func()
Dexuan also showed how the crash can be triggered after introducing
suitable delays in the driver code, thus validating the 'assumption'
that the host can still normally respond to the guest's compose_msi
request after the host has started to eject the PCI device.
Fix the synchronization by leveraging the requestor lock as follows:
- Before 'return'-ing in hv_compose_msi_msg(), remove the ID (while
holding the requestor lock) associated to the completion packet.
- Retrieve the address *and call ->completion_func() within a same
(requestor) critical section in hv_pci_onchannelcallback().
Reported-by: Wei Hu <weh@microsoft.com>
Reported-by: Dexuan Cui <decui@microsoft.com>
Suggested-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lore.kernel.org/r/20220419122325.10078-7-parri.andrea@gmail.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Diffstat (limited to 'net/vmw_vsock/hyperv_transport.c')
0 files changed, 0 insertions, 0 deletions