From e483bb9a991bdae29a0caa4b3a6d002c968f94aa Mon Sep 17 00:00:00 2001
From: Mark Langsdorf <mlangsdo@redhat.com>
Date: Fri, 23 Apr 2021 10:28:17 -0500
Subject: ACPI: custom_method: fix potential use-after-free issue
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 <mlangsdo@redhat.com>
Cc: 5.4+ <stable@vger.kernel.org> # 5.4+
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
drivers/acpi/custom_method.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
(limited to 'drivers/acpi')
diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c
index 443fdf62dd22..8844f895f9be 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;
}
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