| Message ID | 20230216014120.3110-1-k1rh4.lee@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | misc: fastrpc: Fix a Use after-free-bug by race condition | expand |
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 <k1rh4.lee@gmail.com> > --- > 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)
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)
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 <k1rh4.lee@gmail.com> --- drivers/misc/fastrpc.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-)