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kvm: properly check debugfs dentry before using it

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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); 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); char *tmp, *p = kmalloc(PATH_MAX, GFP_KERNEL);
if (p) { if (p) {