* [PATCH 4.14 144/209] kvm: properly check debugfs dentry before using it
[not found] <20191204175321.609072813@linuxfoundation.org>
@ 2019-12-04 17:55 ` Greg Kroah-Hartman
0 siblings, 0 replies; only message in thread
From: Greg Kroah-Hartman @ 2019-12-04 17:55 UTC (permalink / raw)
To: linux-kernel
Cc: Greg Kroah-Hartman, stable, Eric Biggers,
Radim Krčmář,
kvm, Paolo Bonzini, Linus Torvalds, Sasha Levin,
syzbot+7857962b4d45e602b8ad
From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
[ Upstream commit 8ed0579c12b2fe56a1fac2f712f58fc26c1dc49b ]
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 ff9fb72bc077 ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
virt/kvm/kvm_main.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index cdaacdf7bc877..deff4b3eb9722 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -3989,7 +3989,7 @@ 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) {
--
2.20.1
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