Commit 967060d0 authored Aug 14, 2008 by Darrick J. Wong Committed by Ingo Molnar Aug 15, 2008

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 <djwong@us.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent a6825f1c

arch/x86/kernel/msr.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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;
		}

		/*

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