From 967060d00d7ab8e992963a966cd3d18156c02d55 Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Thu, 14 Aug 2008 15:43:33 -0700 Subject: [PATCH] x86, msr: fix NULL pointer deref due to msr_open on nonexistent CPUs msr_open tests for someone trying to open a device for a nonexistent CPU. However, the function always returns 0, not ret like it should, hence userspace can BUG the kernel trivially. This bug was introduced by the cdev lock_kernel pushdown patch last May. The BUG can be reproduced with these commands: # mknod fubar c 202 8 <-- pick a number less than NR_CPUS that is not the number of an online CPU # cat fubar Signed-off-by: Darrick J. Wong Signed-off-by: Ingo Molnar --- arch/x86/kernel/msr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c index 9fd809552447..e43938086885 100644 --- a/arch/x86/kernel/msr.c +++ b/arch/x86/kernel/msr.c @@ -131,7 +131,7 @@ static int msr_open(struct inode *inode, struct file *file) ret = -EIO; /* MSR not supported */ out: unlock_kernel(); - return 0; + return ret; } /*