[PATCH v4 6/9] platform/x86: hp-bioscfg: fix heap OOB with embedded NUL in store paths

[Muhammad Bilal <meatuni001@gmail.com>]

The store handlers copy the input with kstrdup(), which stops at the
first NUL, but pass the full write size to
hp_enforce_single_line_input(). With an embedded NUL the copy is
shorter than count, so the helper reads, and can write one byte, past
the allocation.

Writing "A\0" followed by 4093 bytes of "B" to current_password makes
memchr() scan 4093 bytes past a 2-byte copy. On an HP EliteBook 840 G2
running Linux 7.2.7 all 100 such writes fail with -EINVAL although the
input has no newline, so memchr() matched one in the heap. A userspace
replica under ASan reports the same 4095 byte read, 0 bytes after the
2-byte region.

Use kmemdup_nul() so the copy is always count + 1 bytes long.

Compile tested only.

Fixes: 5f94f181ca25 ("platform/x86: hp-bioscfg: bioscfg-h")
Fixes: 8646a3b5ee3a ("platform/x86: hp-bioscfg: passwdobj-attributes")
Cc: stable@vger.kernel.org
Signed-off-by: Muhammad Bilal <meatuni001@gmail.com>
---
Changes in v4:
 - New patch

 drivers/platform/x86/hp/hp-bioscfg/bioscfg.h              | 2 +-
 drivers/platform/x86/hp/hp-bioscfg/passwdobj-attributes.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/x86/hp/hp-bioscfg/bioscfg.h b/drivers/platform/x86/hp/hp-bioscfg/bioscfg.h
index ac57d6eab..77cb9cac1 100644
--- a/drivers/platform/x86/hp/hp-bioscfg/bioscfg.h
+++ b/drivers/platform/x86/hp/hp-bioscfg/bioscfg.h
@@ -326,7 +326,7 @@ enum hp_wmi_data_elements {
 		int i;							\
 		int ret = -EIO;						\
 									\
-		attr_value = kstrdup(buf, GFP_KERNEL);			\
+		attr_value = kmemdup_nul(buf, count, GFP_KERNEL);	\
 		if (!attr_value)					\
 			return -ENOMEM;					\
 									\
diff --git a/drivers/platform/x86/hp/hp-bioscfg/passwdobj-attributes.c b/drivers/platform/x86/hp/hp-bioscfg/passwdobj-attributes.c
index a2f50ecbe..6c123d7a5 100644
--- a/drivers/platform/x86/hp/hp-bioscfg/passwdobj-attributes.c
+++ b/drivers/platform/x86/hp/hp-bioscfg/passwdobj-attributes.c
@@ -93,7 +93,7 @@ static int store_password_instance(struct kobject *kobj, const char *buf,
 	char *buf_cp;
 	int id, ret = 0;
 
-	buf_cp = kstrdup(buf, GFP_KERNEL);
+	buf_cp = kmemdup_nul(buf, count, GFP_KERNEL);
 	if (!buf_cp)
 		return -ENOMEM;
 
-- 
2.43.0