There are two bug in this code:
1) If count is zero, then it will lead to a NULL dereference. The
kmalloc() will successfully allocate zero bytes and the test for
"if (buf[0] == '-')" will read beyond the end of the zero size buffer
and Oops.
2) The code does not ensure that the user's string is properly NUL
terminated which could lead to a read overflow.
Fortunately, this is debugfs code and only root can write to it so
the security impact of these bugs is negligable.
Fixes: a9996d722b11 ("scsi: scsi_debug: Add interface to manage error injection for a single device")
Signed-off-by: Dan Carpenter <dan.carpenter@xxxxxxxxxx>
---
drivers/scsi/scsi_debug.c | 11 +++--------
1 file changed, 3 insertions(+), 8 deletions(-)
diff --git a/drivers/scsi/scsi_debug.c b/drivers/scsi/scsi_debug.c
index 67922e2c4c19..0a4e41d84df8 100644
--- a/drivers/scsi/scsi_debug.c
+++ b/drivers/scsi/scsi_debug.c
@@ -1019,14 +1019,9 @@ static ssize_t sdebug_error_write(struct file *file, const char __user *ubuf,
struct sdebug_err_inject *inject;
struct scsi_device *sdev = (struct scsi_device *)file->f_inode->i_private;
- buf = kmalloc(count, GFP_KERNEL);
- if (!buf)
- return -ENOMEM;
-
- if (copy_from_user(buf, ubuf, count)) {
- kfree(buf);
- return -EFAULT;
- }
+ buf = strndup_user(ubuf, count + 1);
+ if (IS_ERR(buf))
+ return PTR_ERR(buf);
if (buf[0] == '-')
return sdebug_err_remove(sdev, buf, count);
--
2.42.0
