Reading from /dev/cpu/*/msr with buffer size > 8 would read the data
of the same msr repeatedly instead of the data for consecutive msrs,
as one might expect.
Solve by restricting MSR reads to one per call.
Signed-off-by: Tim Wiederhake <twiederh@xxxxxxxxxx>
---
arch/x86/kernel/msr.c | 21 +++++++--------------
1 file changed, 7 insertions(+), 14 deletions(-)
diff --git a/arch/x86/kernel/msr.c b/arch/x86/kernel/msr.c
index 7bb17d37db01..058f2b67d0c7 100644
--- a/arch/x86/kernel/msr.c
+++ b/arch/x86/kernel/msr.c
@@ -58,24 +58,17 @@ static ssize_t msr_read(struct file *file, char __user *buf,
u32 reg = *ppos;
int cpu = iminor(file_inode(file));
int err = 0;
- ssize_t bytes = 0;
- if (count % 8)
+ if (count < 8)
return -EINVAL; /* Invalid chunk size */
- for (; count; count -= 8) {
- err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);
- if (err)
- break;
- if (copy_to_user(tmp, &data, 8)) {
- err = -EFAULT;
- break;
- }
- tmp += 2;
- bytes += 8;
- }
+ err = rdmsr_safe_on_cpu(cpu, reg, &data[0], &data[1]);
+ if (err)
+ return err;
+ if (copy_to_user(tmp, &data, 8))
+ return -EFAULT;
- return bytes ? bytes : err;
+ return 8;
}
static int filter_write(u32 reg)
--
2.39.2
