[PATCH v2] platform/x86: intel_pmc_core: Uninitialized data in pmc_core_lpm_latch_mode_write()

Dan Carpenter
2021-04-21T15:19:44Z

The simple_write_to_buffer() can return success if even a single byte
is copied from user space. In this case it can result in using
uninitalized data if the buf[] array is not fully initialized. Really
we should only succeed if the whole buffer is copied.

Just using copy_from_user() is simpler and more appropriate.

Fixes: 8074a79fad2e ("platform/x86: intel_pmc_core: Add option to set/clear LPM mode")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
v2: The first version of this patch returned -EINVAL if userspace didn't
give us NUL terminated strings. That's not necessarily a good
assumption.

This patch is just simpler as well. No need to introduce the "len"
variable because "count" is capped at the start of the function.

drivers/platform/x86/intel_pmc_core.c | 8 ++------
1 file changed, 2 insertions(+), 6 deletions(-)

diff --git a/drivers/platform/x86/intel_pmc_core.c b/drivers/platform/x86/intel_pmc_core.c
index d174aeb492e0..b0e486a6bdfb 100644
--- a/drivers/platform/x86/intel_pmc_core.c
+++ b/drivers/platform/x86/intel_pmc_core.c
@@ -1360,17 +1360,13 @@ static ssize_t pmc_core_lpm_latch_mode_write(struct file *file,
struct pmc_dev *pmcdev = s->private;
bool clear = false, c10 = false;
unsigned char buf[8];
- ssize_t ret;
int idx, m, mode;
u32 reg;

if (count > sizeof(buf) - 1)
return -EINVAL;
-
- ret = simple_write_to_buffer(buf, sizeof(buf) - 1, ppos, userbuf, count);
- if (ret < 0)
- return ret;
-
+ if (copy_from_user(buf, userbuf, count))
+ return -EFAULT;
buf[count] = '\0';

/*
--
2.30.2