Some android userspace is sending BINDER_TYPE_FDA objects with
num_fds=0. Like the previous patch, this is reproducible when
playing a video.
Before commit 09184ae9b575 BINDER_TYPE_FDA objects with num_fds=0
were 'correctly handled', as in no fixup was performed.
After commit 09184ae9b575 we aggregate fixup and skip regions in
binder_ptr_fixup structs and distinguish between the two by using
the skip_size field: if it's 0, then it's a fixup, otherwise skip.
When processing BINDER_TYPE_FDA objects with num_fds=0 we add a
skip region of skip_size=0, and this causes issues because now
binder_do_deferred_txn_copies will think this was a fixup region.
To address that, return early from binder_translate_fd_array to
avoid adding an empty skip region.
Fixes: 09184ae9b575 ("binder: defer copies of pre-patched txn data")
Signed-off-by: Alessandro Astone <[email protected]>
---
drivers/android/binder.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 31176edb1069..f3b639e89dd8 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2491,6 +2491,9 @@ static int binder_translate_fd_array(struct list_head *pf_head,
struct binder_proc *proc = thread->proc;
int ret;
+ if (fda->num_fds == 0)
+ return 0;
+
fd_buf_size = sizeof(u32) * fda->num_fds;
if (fda->num_fds >= SIZE_MAX / sizeof(u32)) {
binder_user_error("%d:%d got transaction with invalid number of fds (%lld)\n",
--
2.35.1
When handling BINDER_TYPE_FDA object we are pushing a parent fixup
with a certain skip_size but no scatter-gather copy object, since
the copy is handled standalone.
If BINDER_TYPE_FDA is the last children the scatter-gather copy
loop will never stop to skip it, thus we are left with an item in
the parent fixup list. This will trigger the BUG_ON().
This is reproducible in android when playing a video.
We receive a transaction that looks like this:
obj[0] BINDER_TYPE_PTR, parent
obj[1] BINDER_TYPE_PTR, child
obj[2] BINDER_TYPE_PTR, child
obj[3] BINDER_TYPE_FDA, child
Fixes: 09184ae9b575 ("binder: defer copies of pre-patched txn data")
Signed-off-by: Alessandro Astone <[email protected]>
---
drivers/android/binder.c | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index 8351c5638880..31176edb1069 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -2295,6 +2295,7 @@ static int binder_do_deferred_txn_copies(struct binder_alloc *alloc,
{
int ret = 0;
struct binder_sg_copy *sgc, *tmpsgc;
+ struct binder_ptr_fixup *tmppf;
struct binder_ptr_fixup *pf =
list_first_entry_or_null(pf_head, struct binder_ptr_fixup,
node);
@@ -2349,7 +2350,11 @@ static int binder_do_deferred_txn_copies(struct binder_alloc *alloc,
list_del(&sgc->node);
kfree(sgc);
}
- BUG_ON(!list_empty(pf_head));
+ list_for_each_entry_safe(pf, tmppf, pf_head, node) {
+ BUG_ON(pf->skip_size == 0);
+ list_del(&pf->node);
+ kfree(pf);
+ }
BUG_ON(!list_empty(sgc_head));
return ret > 0 ? -EINVAL : ret;
--
2.35.1
On Fri, Apr 15, 2022 at 5:00 AM Alessandro Astone <[email protected]> wrote:
>
> Some android userspace is sending BINDER_TYPE_FDA objects with
> num_fds=0. Like the previous patch, this is reproducible when
> playing a video.
>
> Before commit 09184ae9b575 BINDER_TYPE_FDA objects with num_fds=0
> were 'correctly handled', as in no fixup was performed.
>
> After commit 09184ae9b575 we aggregate fixup and skip regions in
> binder_ptr_fixup structs and distinguish between the two by using
> the skip_size field: if it's 0, then it's a fixup, otherwise skip.
> When processing BINDER_TYPE_FDA objects with num_fds=0 we add a
> skip region of skip_size=0, and this causes issues because now
> binder_do_deferred_txn_copies will think this was a fixup region.
>
> To address that, return early from binder_translate_fd_array to
> avoid adding an empty skip region.
>
> Fixes: 09184ae9b575 ("binder: defer copies of pre-patched txn data")
> Signed-off-by: Alessandro Astone <[email protected]>
Acked-by: Todd Kjos <[email protected]>
> ---
> drivers/android/binder.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 31176edb1069..f3b639e89dd8 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -2491,6 +2491,9 @@ static int binder_translate_fd_array(struct list_head *pf_head,
> struct binder_proc *proc = thread->proc;
> int ret;
>
> + if (fda->num_fds == 0)
> + return 0;
> +
> fd_buf_size = sizeof(u32) * fda->num_fds;
> if (fda->num_fds >= SIZE_MAX / sizeof(u32)) {
> binder_user_error("%d:%d got transaction with invalid number of fds (%lld)\n",
> --
> 2.35.1
>
On Fri, Apr 15, 2022 at 5:00 AM Alessandro Astone <[email protected]> wrote:
>
> When handling BINDER_TYPE_FDA object we are pushing a parent fixup
> with a certain skip_size but no scatter-gather copy object, since
> the copy is handled standalone.
> If BINDER_TYPE_FDA is the last children the scatter-gather copy
> loop will never stop to skip it, thus we are left with an item in
> the parent fixup list. This will trigger the BUG_ON().
>
> This is reproducible in android when playing a video.
> We receive a transaction that looks like this:
> obj[0] BINDER_TYPE_PTR, parent
> obj[1] BINDER_TYPE_PTR, child
> obj[2] BINDER_TYPE_PTR, child
> obj[3] BINDER_TYPE_FDA, child
>
> Fixes: 09184ae9b575 ("binder: defer copies of pre-patched txn data")
> Signed-off-by: Alessandro Astone <[email protected]>
Acked-by: Todd Kjos <[email protected]>
> ---
> drivers/android/binder.c | 7 ++++++-
> 1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 8351c5638880..31176edb1069 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -2295,6 +2295,7 @@ static int binder_do_deferred_txn_copies(struct binder_alloc *alloc,
> {
> int ret = 0;
> struct binder_sg_copy *sgc, *tmpsgc;
> + struct binder_ptr_fixup *tmppf;
> struct binder_ptr_fixup *pf =
> list_first_entry_or_null(pf_head, struct binder_ptr_fixup,
> node);
> @@ -2349,7 +2350,11 @@ static int binder_do_deferred_txn_copies(struct binder_alloc *alloc,
> list_del(&sgc->node);
> kfree(sgc);
> }
> - BUG_ON(!list_empty(pf_head));
> + list_for_each_entry_safe(pf, tmppf, pf_head, node) {
> + BUG_ON(pf->skip_size == 0);
> + list_del(&pf->node);
> + kfree(pf);
> + }
> BUG_ON(!list_empty(sgc_head));
>
> return ret > 0 ? -EINVAL : ret;
> --
> 2.35.1
>