summaryrefslogtreecommitdiffstats
diff options
context:
space:
mode:
authorEric Biggers <ebiggers@google.com>2018-02-01 02:30:21 +0100
committerPaolo Bonzini <pbonzini@redhat.com>2018-02-24 01:43:35 +0100
commit103c763c72dd2df3e8c91f2d7ec88f98ed391111 (patch)
tree970cb89a636c7437bf15fab6e8223b73c58a2ee4
parentKVM: nVMX: preserve SECONDARY_EXEC_DESC without UMIP (diff)
downloadlinux-103c763c72dd2df3e8c91f2d7ec88f98ed391111.tar.xz
linux-103c763c72dd2df3e8c91f2d7ec88f98ed391111.zip
KVM/x86: remove WARN_ON() for when vm_munmap() fails
On x86, special KVM memslots such as the TSS region have anonymous memory mappings created on behalf of userspace, and these mappings are removed when the VM is destroyed. It is however possible for removing these mappings via vm_munmap() to fail. This can most easily happen if the thread receives SIGKILL while it's waiting to acquire ->mmap_sem. This triggers the 'WARN_ON(r < 0)' in __x86_set_memory_region(). syzkaller was able to hit this, using 'exit()' to send the SIGKILL. Note that while the vm_munmap() failure results in the mapping not being removed immediately, it is not leaked forever but rather will be freed when the process exits. It's not really possible to handle this failure properly, so almost every other caller of vm_munmap() doesn't check the return value. It's a limitation of having the kernel manage these mappings rather than userspace. So just remove the WARN_ON() so that users can't spam the kernel log with this warning. Fixes: f0d648bdf0a5 ("KVM: x86: map/unmap private slots in __x86_set_memory_region") Reported-by: syzbot <syzkaller@googlegroups.com> Signed-off-by: Eric Biggers <ebiggers@google.com> Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
-rw-r--r--arch/x86/kvm/x86.c6
1 files changed, 2 insertions, 4 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index ca90d9515137..96edda878dbf 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8461,10 +8461,8 @@ int __x86_set_memory_region(struct kvm *kvm, int id, gpa_t gpa, u32 size)
return r;
}
- if (!size) {
- r = vm_munmap(old.userspace_addr, old.npages * PAGE_SIZE);
- WARN_ON(r < 0);
- }
+ if (!size)
+ vm_munmap(old.userspace_addr, old.npages * PAGE_SIZE);
return 0;
}