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kvm: properly check debugfs dentry before using it 

debugfs can now report an error code if something went wrong instead of
just NULL.  So if the return value is to be used as a "real" dentry, it
needs to be checked if it is an error before dereferencing it.

This is now happening because of ff9fb72bc0 ("debugfs: return error
values, not NULL").  syzbot has found a way to trigger multiple debugfs
files attempting to be created, which fails, and then the error code
gets passed to dentry_path_raw() which obviously does not like it.

Reported-by: Eric Biggers <ebiggers@kernel.org>
Reported-and-tested-by: syzbot+7857962b4d45e602b8ad@syzkaller.appspotmail.com
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: kvm@vger.kernel.org
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Greg Kroah-Hartman 2019-02-28 16:34:37 +01:00 committed by Linus Torvalds
parent 0a1d52994d
commit 8ed0579c12
1 changed files with 1 additions and 1 deletions
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2
virt/kvm/kvm_main.c
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@ -4044,7 +4044,7 @@ static void kvm_uevent_notify_change(unsigned int type, struct kvm *kvm)
}
add_uevent_var(env, "PID=%d", kvm->userspace_pid);
if (kvm->debugfs_dentry) {
if (!IS_ERR_OR_NULL(kvm->debugfs_dentry)) {
char *tmp, *p = kmalloc(PATH_MAX, GFP_KERNEL);
if (p) {