From 62dc2440ebb552aa0d7f635e1697e077d9d21203 Mon Sep 17 00:00:00 2001 From: Mark Langsdorf Date: Fri, 23 Apr 2021 10:28:17 -0500 Subject: [PATCH] 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(-) diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c index 7b54dc95d36b..fa9f7ff4a3a6 100644 --- a/drivers/acpi/custom_method.c +++ b/drivers/acpi/custom_method.c @@ -55,6 +55,7 @@ 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; } @@ -76,7 +77,6 @@ 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; } -- 2.25.1