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Subject[PATCH] binder: fix incorrect calculation for num_valid
Date
For BINDER_TYPE_PTR and BINDER_TYPE_FDA transactions, the
num_valid local was calculated incorrectly causing the
range check in binder_validate_ptr() to miss out-of-bounds
offsets.

Fixes: bde4a19fc04f ("binder: use userspace pointer as base of buffer space")
Signed-off-by: Todd Kjos <tkjos@google.com>
---
drivers/android/binder.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index e9bc9fcc7ea5..b2dad43dbf82 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -3310,7 +3310,7 @@ static void binder_transaction(struct binder_proc *proc,
binder_size_t parent_offset;
struct binder_fd_array_object *fda =
to_binder_fd_array_object(hdr);
- size_t num_valid = (buffer_offset - off_start_offset) *
+ size_t num_valid = (buffer_offset - off_start_offset) /
sizeof(binder_size_t);
struct binder_buffer_object *parent =
binder_validate_ptr(target_proc, t->buffer,
@@ -3384,7 +3384,7 @@ static void binder_transaction(struct binder_proc *proc,
t->buffer->user_data + sg_buf_offset;
sg_buf_offset += ALIGN(bp->length, sizeof(u64));

- num_valid = (buffer_offset - off_start_offset) *
+ num_valid = (buffer_offset - off_start_offset) /
sizeof(binder_size_t);
ret = binder_fixup_parent(t, thread, bp,
off_start_offset,
--
2.24.1.735.g03f4e72817-goog
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