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;
}
/*
--
