[PATCH 5.10 329/545] eeprom: idt_89hpesx: uninitialized data in idt_dbgfs_csr_write()

Greg Kroah-Hartman
2022-08-19T16:27:19Z

From: Dan Carpenter <dan.carpenter@oracle.com>

[ Upstream commit 71d46f1ff2212ced4852c7e77c5176382a1bdcec ]

The simple_write_to_buffer() function will return positive/success if it
is able to write a single byte anywhere within the buffer. However that
potentially leaves a lot of the buffer uninitialized.

In this code it's better to return 0 if the offset is non-zero. This
code is not written to support partial writes. And then return -EFAULT
if the buffer is not completely initialized.

Fixes: cfad6425382e ("eeprom: Add IDT 89HPESx EEPROM/CSR driver")
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/Ysg1Pu/nzSMe3r1q@kili
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/misc/eeprom/idt_89hpesx.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/drivers/misc/eeprom/idt_89hpesx.c b/drivers/misc/eeprom/idt_89hpesx.c
index 3e4a594c110b..6a456645efb0 100644
--- a/drivers/misc/eeprom/idt_89hpesx.c
+++ b/drivers/misc/eeprom/idt_89hpesx.c
@@ -940,14 +940,18 @@ static ssize_t idt_dbgfs_csr_write(struct file *filep, const char __user *ubuf,
u32 csraddr, csrval;
char *buf;

+ if (*offp)
+ return 0;
+
/* Copy data from User-space */
buf = kmalloc(count + 1, GFP_KERNEL);
if (!buf)
return -ENOMEM;

- ret = simple_write_to_buffer(buf, count, offp, ubuf, count);
- if (ret < 0)
+ if (copy_from_user(buf, ubuf, count)) {
+ ret = -EFAULT;
goto free_buf;
+ }
buf[count] = 0;

/* Find position of colon in the buffer */
--
2.35.1