From 1d53ca5d131074c925ce38361fb0376d3bf7e394 Mon Sep 17 00:00:00 2001 From: Mark Langsdorf Date: Fri, 23 Apr 2021 10:28:17 -0500 Subject: ACPI: custom_method: fix potential use-after-free issue commit e483bb9a991bdae29a0caa4b3a6d002c968f94aa upstream. In cm_write(), buf is always freed when reaching the end of the function. If the requested count is less than table.length, the allocated buffer will be freed but subsequent calls to cm_write() will still try to access it. Remove the unconditional kfree(buf) at the end of the function and set the buf to NULL in the -EINVAL error path to match the rest of function. Fixes: 03d1571d9513 ("ACPI: custom_method: fix memory leaks") Signed-off-by: Mark Langsdorf Cc: 5.4+ # 5.4+ Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman --- drivers/acpi/custom_method.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'drivers/acpi/custom_method.c') diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c index 435bd0ffc8c0..c76ab507c182 100644 --- a/drivers/acpi/custom_method.c +++ b/drivers/acpi/custom_method.c @@ -50,6 +50,7 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf, (*ppos + count < count) || (count > uncopied_bytes)) { kfree(buf); + buf = NULL; return -EINVAL; } @@ -71,7 +72,6 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf, add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE); } - kfree(buf); return count; } -- cgit v1.2.3 From 3a0cadd433491b7277fc38d100fdce0fddddd983 Mon Sep 17 00:00:00 2001 From: Mark Langsdorf Date: Tue, 27 Apr 2021 13:54:33 -0500 Subject: ACPI: custom_method: fix a possible memory leak commit 1cfd8956437f842836e8a066b40d1ec2fc01f13e upstream. In cm_write(), if the 'buf' is allocated memory but not fully consumed, it is possible to reallocate the buffer without freeing it by passing '*ppos' as 0 on a subsequent call. Add an explicit kfree() before kzalloc() to prevent the possible memory leak. Fixes: 526b4af47f44 ("ACPI: Split out custom_method functionality into an own driver") Signed-off-by: Mark Langsdorf Cc: 5.4+ # 5.4+ Signed-off-by: Rafael J. Wysocki Signed-off-by: Greg Kroah-Hartman --- drivers/acpi/custom_method.c | 2 ++ 1 file changed, 2 insertions(+) (limited to 'drivers/acpi/custom_method.c') diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c index c76ab507c182..ea4c7c93a920 100644 --- a/drivers/acpi/custom_method.c +++ b/drivers/acpi/custom_method.c @@ -37,6 +37,8 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf, sizeof(struct acpi_table_header))) return -EFAULT; uncopied_bytes = max_size = table.length; + /* make sure the buf is not allocated */ + kfree(buf); buf = kzalloc(max_size, GFP_KERNEL); if (!buf) return -ENOMEM; -- cgit v1.2.3