103c763c72
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>
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.