2023-02-16 01:42:38

by sangsup lee

Subject: [PATCH] misc: fastrpc: Fix a Use after-free-bug by race condition

This patch adds mutex_lock for fixing an Use-after-free bug.
fastrpc_req_munmap_impl can be called concurrently in multi-threded environments.
The buf which is allocated by list_for_each_safe can be used after another thread frees it.

Signed-off-by: Sangsup Lee <[email protected]>
---
drivers/misc/fastrpc.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index 5310606113fe..c4b5fa4a50a6 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -1806,10 +1806,12 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp)
struct fastrpc_buf *buf = NULL, *iter, *b;
struct fastrpc_req_munmap req;
struct device *dev = fl->sctx->dev;
+ int err;

if (copy_from_user(&req, argp, sizeof(req)))
return -EFAULT;

+ mutex_lock(&fl->mutex);
spin_lock(&fl->lock);
list_for_each_entry_safe(iter, b, &fl->mmaps, node) {
if ((iter->raddr == req.vaddrout) && (iter->size == req.size)) {
@@ -1822,10 +1824,13 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp)
if (!buf) {
dev_err(dev, "mmap\t\tpt 0x%09llx [len 0x%08llx] not in list\n",
req.vaddrout, req.size);
+ mutex_unlock(&fl->mutex);
return -EINVAL;
}

- return fastrpc_req_munmap_impl(fl, buf);
+ err = fastrpc_req_munmap_impl(fl, buf);
+ mutex_unlock(&fl->mutex);
+ return err;
}

static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
--
2.25.1

2023-02-16 01:54:23

by sangsup lee

Subject: Re: [PATCH] misc: fastrpc: Fix a Use after-free-bug by race condition

As I'm not an expert for the fastrpc driver, I'm not sure about the patch code.
But I think the bug should be patched.
Please suggest a proper patch.

Best regards,

2023년 2월 16일 (목) 오전 10:41, Sangsup Lee <[email protected]>님이 작성:
>
> This patch adds mutex_lock for fixing an Use-after-free bug.
> fastrpc_req_munmap_impl can be called concurrently in multi-threded environments.
> The buf which is allocated by list_for_each_safe can be used after another thread frees it.
>
> Signed-off-by: Sangsup Lee <[email protected]>
> ---
> drivers/misc/fastrpc.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index 5310606113fe..c4b5fa4a50a6 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -1806,10 +1806,12 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp)
> struct fastrpc_buf *buf = NULL, *iter, *b;
> struct fastrpc_req_munmap req;
> struct device *dev = fl->sctx->dev;
> + int err;
>
> if (copy_from_user(&req, argp, sizeof(req)))
> return -EFAULT;
>
> + mutex_lock(&fl->mutex);
> spin_lock(&fl->lock);
> list_for_each_entry_safe(iter, b, &fl->mmaps, node) {
> if ((iter->raddr == req.vaddrout) && (iter->size == req.size)) {
> @@ -1822,10 +1824,13 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp)
> if (!buf) {
> dev_err(dev, "mmap\t\tpt 0x%09llx [len 0x%08llx] not in list\n",
> req.vaddrout, req.size);
> + mutex_unlock(&fl->mutex);
> return -EINVAL;
> }
>
> - return fastrpc_req_munmap_impl(fl, buf);
> + err = fastrpc_req_munmap_impl(fl, buf);
> + mutex_unlock(&fl->mutex);
> + return err;
> }
>
> static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)
> --
> 2.25.1
>

2023-03-21 09:27:54

by Srinivas Kandagatla

Subject: Re: [PATCH] misc: fastrpc: Fix a Use after-free-bug by race condition

Thanks Sangsup for reporting the issue and sharing the patch,

Sorry, for some reason I missed this patch.

On 16/02/2023 01:41, Sangsup Lee wrote:
> This patch adds mutex_lock for fixing an Use-after-free bug.
> fastrpc_req_munmap_impl can be called concurrently in multi-threded environments.
> The buf which is allocated by list_for_each_safe can be used after another thread frees it.
>
Commit log can be improved here to something like:

fastrcp_munmap takes two steps to unmap the memory, first to find a
matching fastrpc buf in the list and second is to send request to DSP to
unmap it.
There is a potentially window of race between these two operations,
which can lead to user-after-free.

Fix this by adding locking around this two operations.

> Signed-off-by: Sangsup Lee <[email protected]>
> ---
> drivers/misc/fastrpc.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index 5310606113fe..c4b5fa4a50a6 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -1806,10 +1806,12 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp)
> struct fastrpc_buf *buf = NULL, *iter, *b;
> struct fastrpc_req_munmap req;
> struct device *dev = fl->sctx->dev;
> + int err;
>
> if (copy_from_user(&req, argp, sizeof(req)))
> return -EFAULT;
>
> + mutex_lock(&fl->mutex);
> spin_lock(&fl->lock);
> list_for_each_entry_safe(iter, b, &fl->mmaps, node) {
> if ((iter->raddr == req.vaddrout) && (iter->size == req.size)) {
> @@ -1822,10 +1824,13 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp)
> if (!buf) {
> dev_err(dev, "mmap\t\tpt 0x%09llx [len 0x%08llx] not in list\n",
> req.vaddrout, req.size);
> + mutex_unlock(&fl->mutex);
> return -EINVAL;
> }
>
> - return fastrpc_req_munmap_impl(fl, buf);
> + err = fastrpc_req_munmap_impl(fl, buf);
> + mutex_unlock(&fl->mutex);
> + return err;

How about moving the locking to ioctl:

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index a701132638cf..2f217071a6c3 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -2087,7 +2087,9 @@ static long fastrpc_device_ioctl(struct file
*file, unsigned int cmd,
err = fastrpc_req_mmap(fl, argp);
break;
case FASTRPC_IOCTL_MUNMAP:
+ mutex_lock(&fl->mutex);
err = fastrpc_req_munmap(fl, argp);
+ mutex_unlock(&fl->mutex);
break;
case FASTRPC_IOCTL_MEM_MAP:
err = fastrpc_req_mem_map(fl, argp);


thanks,
srini
> }
>
> static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)

2023-03-22 02:03:03

by sangsup lee

Subject: Re: [PATCH] misc: fastrpc: Fix a Use after-free-bug by race condition

Sounds great.

Thank you for your recommendation.
The patch code that you recommend is clear and simple.
Please patch this.

Signed-off-by: Sangsup lee <[email protected]>
---
drivers/misc/fastrpc.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
index 93ebd174d848..aa1cf0e9f4ed 100644
--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -1901,7 +1901,9 @@ static long fastrpc_device_ioctl(struct file
*file, unsigned int cmd,
err = fastrpc_req_mmap(fl, argp);
break;
case FASTRPC_IOCTL_MUNMAP:
+ mutex_lock(&fl->mutex);
err = fastrpc_req_munmap(fl, argp);
+ mutex_unlock(&fl->mutex);
break;
case FASTRPC_IOCTL_MEM_MAP:
err = fastrpc_req_mem_map(fl, argp);
--
2.25.1


2023년 3월 21일 (화) 오후 6:27, Srinivas Kandagatla
<[email protected]>님이 작성:
>
> Thanks Sangsup for reporting the issue and sharing the patch,
>
> Sorry, for some reason I missed this patch.
>
> On 16/02/2023 01:41, Sangsup Lee wrote:
> > This patch adds mutex_lock for fixing an Use-after-free bug.
> > fastrpc_req_munmap_impl can be called concurrently in multi-threded environments.
> > The buf which is allocated by list_for_each_safe can be used after another thread frees it.
> >
> Commit log can be improved here to something like:
>
> fastrcp_munmap takes two steps to unmap the memory, first to find a
> matching fastrpc buf in the list and second is to send request to DSP to
> unmap it.
> There is a potentially window of race between these two operations,
> which can lead to user-after-free.
>
> Fix this by adding locking around this two operations.
>
> > Signed-off-by: Sangsup Lee <[email protected]>
> > ---
> > drivers/misc/fastrpc.c | 7 ++++++-
> > 1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> > index 5310606113fe..c4b5fa4a50a6 100644
> > --- a/drivers/misc/fastrpc.c
> > +++ b/drivers/misc/fastrpc.c
> > @@ -1806,10 +1806,12 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp)
> > struct fastrpc_buf *buf = NULL, *iter, *b;
> > struct fastrpc_req_munmap req;
> > struct device *dev = fl->sctx->dev;
> > + int err;
> >
> > if (copy_from_user(&req, argp, sizeof(req)))
> > return -EFAULT;
> >
> > + mutex_lock(&fl->mutex);
> > spin_lock(&fl->lock);
> > list_for_each_entry_safe(iter, b, &fl->mmaps, node) {
> > if ((iter->raddr == req.vaddrout) && (iter->size == req.size)) {
> > @@ -1822,10 +1824,13 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp)
> > if (!buf) {
> > dev_err(dev, "mmap\t\tpt 0x%09llx [len 0x%08llx] not in list\n",
> > req.vaddrout, req.size);
> > + mutex_unlock(&fl->mutex);
> > return -EINVAL;
> > }
> >
> > - return fastrpc_req_munmap_impl(fl, buf);
> > + err = fastrpc_req_munmap_impl(fl, buf);
> > + mutex_unlock(&fl->mutex);
> > + return err;
>
> How about moving the locking to ioctl:
>
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index a701132638cf..2f217071a6c3 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -2087,7 +2087,9 @@ static long fastrpc_device_ioctl(struct file
> *file, unsigned int cmd,
> err = fastrpc_req_mmap(fl, argp);
> break;
> case FASTRPC_IOCTL_MUNMAP:
> + mutex_lock(&fl->mutex);
> err = fastrpc_req_munmap(fl, argp);
> + mutex_unlock(&fl->mutex);
> break;
> case FASTRPC_IOCTL_MEM_MAP:
> err = fastrpc_req_mem_map(fl, argp);
>
>
> thanks,
> srini
> > }
> >
> > static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)

2023-03-22 08:48:23

by Srinivas Kandagatla

Subject: Re: [PATCH] misc: fastrpc: Fix a Use after-free-bug by race condition

On 22/03/2023 01:59, sangsup lee wrote:
> Sounds great.
>
> Thank you for your recommendation.
> The patch code that you recommend is clear and simple.
> Please patch this.
>
> Signed-off-by: Sangsup lee <[email protected]>
> ---

Please follow kernel patch submission guidelines, any changes to code
should be send as new version of patch.

Have a look at Documentation/process/submitting-patches.rst for more
information.

thanks,
Srini
> drivers/misc/fastrpc.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> index 93ebd174d848..aa1cf0e9f4ed 100644
> --- a/drivers/misc/fastrpc.c
> +++ b/drivers/misc/fastrpc.c
> @@ -1901,7 +1901,9 @@ static long fastrpc_device_ioctl(struct file
> *file, unsigned int cmd,
> err = fastrpc_req_mmap(fl, argp);
> break;
> case FASTRPC_IOCTL_MUNMAP:
> + mutex_lock(&fl->mutex);
> err = fastrpc_req_munmap(fl, argp);
> + mutex_unlock(&fl->mutex);
> break;
> case FASTRPC_IOCTL_MEM_MAP:
> err = fastrpc_req_mem_map(fl, argp);
> --
> 2.25.1
>
>
> 2023년 3월 21일 (화) 오후 6:27, Srinivas Kandagatla
> <[email protected]>님이 작성:
>>
>> Thanks Sangsup for reporting the issue and sharing the patch,
>>
>> Sorry, for some reason I missed this patch.
>>
>> On 16/02/2023 01:41, Sangsup Lee wrote:
>>> This patch adds mutex_lock for fixing an Use-after-free bug.
>>> fastrpc_req_munmap_impl can be called concurrently in multi-threded environments.
>>> The buf which is allocated by list_for_each_safe can be used after another thread frees it.
>>>
>> Commit log can be improved here to something like:
>>
>> fastrcp_munmap takes two steps to unmap the memory, first to find a
>> matching fastrpc buf in the list and second is to send request to DSP to
>> unmap it.
>> There is a potentially window of race between these two operations,
>> which can lead to user-after-free.
>>
>> Fix this by adding locking around this two operations.
>>
>>> Signed-off-by: Sangsup Lee <[email protected]>
>>> ---
>>> drivers/misc/fastrpc.c | 7 ++++++-
>>> 1 file changed, 6 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
>>> index 5310606113fe..c4b5fa4a50a6 100644
>>> --- a/drivers/misc/fastrpc.c
>>> +++ b/drivers/misc/fastrpc.c
>>> @@ -1806,10 +1806,12 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp)
>>> struct fastrpc_buf *buf = NULL, *iter, *b;
>>> struct fastrpc_req_munmap req;
>>> struct device *dev = fl->sctx->dev;
>>> + int err;
>>>
>>> if (copy_from_user(&req, argp, sizeof(req)))
>>> return -EFAULT;
>>>
>>> + mutex_lock(&fl->mutex);
>>> spin_lock(&fl->lock);
>>> list_for_each_entry_safe(iter, b, &fl->mmaps, node) {
>>> if ((iter->raddr == req.vaddrout) && (iter->size == req.size)) {
>>> @@ -1822,10 +1824,13 @@ static int fastrpc_req_munmap(struct fastrpc_user *fl, char __user *argp)
>>> if (!buf) {
>>> dev_err(dev, "mmap\t\tpt 0x%09llx [len 0x%08llx] not in list\n",
>>> req.vaddrout, req.size);
>>> + mutex_unlock(&fl->mutex);
>>> return -EINVAL;
>>> }
>>>
>>> - return fastrpc_req_munmap_impl(fl, buf);
>>> + err = fastrpc_req_munmap_impl(fl, buf);
>>> + mutex_unlock(&fl->mutex);
>>> + return err;
>>
>> How about moving the locking to ioctl:
>>
>> diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
>> index a701132638cf..2f217071a6c3 100644
>> --- a/drivers/misc/fastrpc.c
>> +++ b/drivers/misc/fastrpc.c
>> @@ -2087,7 +2087,9 @@ static long fastrpc_device_ioctl(struct file
>> *file, unsigned int cmd,
>> err = fastrpc_req_mmap(fl, argp);
>> break;
>> case FASTRPC_IOCTL_MUNMAP:
>> + mutex_lock(&fl->mutex);
>> err = fastrpc_req_munmap(fl, argp);
>> + mutex_unlock(&fl->mutex);
>> break;
>> case FASTRPC_IOCTL_MEM_MAP:
>> err = fastrpc_req_mem_map(fl, argp);
>>
>>
>> thanks,
>> srini
>>> }
>>>
>>> static int fastrpc_req_mmap(struct fastrpc_user *fl, char __user *argp)