From: Jim Lin <[email protected]>
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.
Signed-off-by: Jim Lin <[email protected]>
Signed-off-by: Macpaul Lin <[email protected]>
Cc: [email protected]
---
Changes in v2:
Changes in v3:
- Change commit description
Changes in v4:
- Fix build error and adapt patch to kernel-5.12-rc1.
Replace definition "MAX_USB_STRING_WITH_NULL_LEN" with
"USB_MAX_STRING_WITH_NULL_LEN".
- Note: The patch v2 and v3 has been verified by
Thadeu Lima de Souza Cascardo <[email protected]>
http://spinics.net/lists/kernel/msg3840792.html
and
Macpaul Lin <[email protected]> on Android kernels.
http://lkml.org/lkml/2020/6/11/8
- The patch is suggested to be applied to LTS versions.
drivers/usb/gadget/configfs.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)
diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c
index 0d56f33..15a607c 100644
--- 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, char **s_copy)
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;
}
--
1.7.9.5
On Thu, 2021-03-11 at 14:42 +0800, Macpaul Lin wrote:
> From: Jim Lin <[email protected]>
>
> 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.
>
> Signed-off-by: Jim Lin <[email protected]>
> Signed-off-by: Macpaul Lin <[email protected]>
> Cc: [email protected]
> ---
> Changes in v2:
> Changes in v3:
> - Change commit description
> Changes in v4:
> - Fix build error and adapt patch to kernel-5.12-rc1.
> Replace definition "MAX_USB_STRING_WITH_NULL_LEN" with
> "USB_MAX_STRING_WITH_NULL_LEN".
> - Note: The patch v2 and v3 has been verified by
> Thadeu Lima de Souza Cascardo <[email protected]>
> http://spinics.net/lists/kernel/msg3840792.html
Dear Cascardo,
Would you please help to confirm if you've tested it on Linux PC,
Chrome OS, or an Android OS?
Thanks!
Macpaul Lin
> and
> Macpaul Lin <[email protected]> on Android kernels.
> http://lkml.org/lkml/2020/6/11/8
> - The patch is suggested to be applied to LTS versions.
>
> drivers/usb/gadget/configfs.c | 14 ++++++++++----
> 1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c
> index 0d56f33..15a607c 100644
> --- 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, char **s_copy)
> 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;
> }
On Thu, Mar 11, 2021 at 02:53:52PM +0800, Macpaul Lin wrote:
> On Thu, 2021-03-11 at 14:42 +0800, Macpaul Lin wrote:
> > From: Jim Lin <[email protected]>
> >
> > 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.
> >
> > Signed-off-by: Jim Lin <[email protected]>
> > Signed-off-by: Macpaul Lin <[email protected]>
> > Cc: [email protected]
> > ---
> > Changes in v2:
> > Changes in v3:
> > - Change commit description
> > Changes in v4:
> > - Fix build error and adapt patch to kernel-5.12-rc1.
> > Replace definition "MAX_USB_STRING_WITH_NULL_LEN" with
> > "USB_MAX_STRING_WITH_NULL_LEN".
> > - Note: The patch v2 and v3 has been verified by
> > Thadeu Lima de Souza Cascardo <[email protected]>
> > http://spinics.net/lists/kernel/msg3840792.html
>
> Dear Cascardo,
>
> Would you please help to confirm if you've tested it on Linux PC,
> Chrome OS, or an Android OS?
I tested v3 on Ubuntu GNU/Linux. I will test v4.
Cascardo.
>
> Thanks!
> Macpaul Lin
>
> > and
> > Macpaul Lin <[email protected]> on Android kernels.
> > http://lkml.org/lkml/2020/6/11/8
> > - The patch is suggested to be applied to LTS versions.
> >
> > drivers/usb/gadget/configfs.c | 14 ++++++++++----
> > 1 file changed, 10 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/usb/gadget/configfs.c b/drivers/usb/gadget/configfs.c
> > index 0d56f33..15a607c 100644
> > --- 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, char **s_copy)
> > 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;
> > }
>