Messages in this thread Patch in this message | | | Date | Thu, 14 Aug 2008 15:43:33 -0700 | From | "Darrick J. Wong" <> | Subject | [PATCH] msr: Fix NULL pointer deref due to msr_open on nonexistent CPUs |
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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> ---
arch/x86/kernel/msr.c | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c index 9fd8095..e439380 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; } /*
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