This is a note to let you know that I've just added the patch titled
usb: gadget: configfs: Fix KASAN use-after-free
to the 5.11-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
usb-gadget-configfs-fix-kasan-use-after-free.patch
and it can be found in the queue-5.11 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 98f153a10da403ddd5e9d98a3c8c2bb54bb5a0b6 Mon Sep 17 00:00:00 2001
From: Jim Lin <jilin@xxxxxxxxxx>
Date: Thu, 11 Mar 2021 14:42:41 +0800
Subject: usb: gadget: configfs: Fix KASAN use-after-free
From: Jim Lin <jilin@xxxxxxxxxx>
commit 98f153a10da403ddd5e9d98a3c8c2bb54bb5a0b6 upstream.
When gadget is disconnected, running sequence is like this.
. composite_disconnect
. Call trace:
usb_string_copy+0xd0/0x128
gadget_config_name_configuration_store+0x4
gadget_config_name_attr_store+0x40/0x50
configfs_write_file+0x198/0x1f4
vfs_write+0x100/0x220
SyS_write+0x58/0xa8
. configfs_composite_unbind
. configfs_composite_bind
In configfs_composite_bind, it has
"cn->strings.s = cn->configuration;"
When usb_string_copy is invoked. it would
allocate memory, copy input string, release previous pointed memory space,
and use new allocated memory.
When gadget is connected, host sends down request to get information.
Call trace:
usb_gadget_get_string+0xec/0x168
lookup_string+0x64/0x98
composite_setup+0xa34/0x1ee8
If gadget is disconnected and connected quickly, in the failed case,
cn->configuration memory has been released by usb_string_copy kfree but
configfs_composite_bind hasn't been run in time to assign new allocated
"cn->configuration" pointer to "cn->strings.s".
When "strlen(s->s) of usb_gadget_get_string is being executed, the dangling
memory is accessed, "BUG: KASAN: use-after-free" error occurs.
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Jim Lin <jilin@xxxxxxxxxx>
Signed-off-by: Macpaul Lin <macpaul.lin@xxxxxxxxxxxx>
Link: https://lore.kernel.org/r/1615444961-13376-1-git-send-email-macpaul.lin@xxxxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/usb/gadget/configfs.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
--- a/drivers/usb/gadget/configfs.c
+++ b/drivers/usb/gadget/configfs.c
@@ -97,6 +97,8 @@ struct gadget_config_name {
struct list_head list;
};
+#define USB_MAX_STRING_WITH_NULL_LEN (USB_MAX_STRING_LEN+1)
+
static int usb_string_copy(const char *s, char **s_copy)
{
int ret;
@@ -106,12 +108,16 @@ static int usb_string_copy(const char *s
if (ret > USB_MAX_STRING_LEN)
return -EOVERFLOW;
- str = kstrdup(s, GFP_KERNEL);
- if (!str)
- return -ENOMEM;
+ if (copy) {
+ str = copy;
+ } else {
+ str = kmalloc(USB_MAX_STRING_WITH_NULL_LEN, GFP_KERNEL);
+ if (!str)
+ return -ENOMEM;
+ }
+ strcpy(str, s);
if (str[ret - 1] == '\n')
str[ret - 1] = '\0';
- kfree(copy);
*s_copy = str;
return 0;
}
Patches currently in stable-queue which might be from jilin@xxxxxxxxxx are
queue-5.11/usb-gadget-configfs-fix-kasan-use-after-free.patch
