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From: Todd Kjos <>
Subject: [PATCH] binder: fix incorrect calculation for num_valid
Date: Fri, 13 Dec 2019 12:25:31 -0800
Message-ID: <> (raw)

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

Fixes: bde4a19fc04f ("binder: use userspace pointer as base of buffer space")
Signed-off-by: Todd Kjos <>
 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 =
-			size_t num_valid = (buffer_offset - off_start_offset) *
+			size_t num_valid = (buffer_offset - off_start_offset) /
 			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) /
 			ret = binder_fixup_parent(t, thread, bp,

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