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binder: fix incorrect calculation for num_valid

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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: bde4a19fc0 ("binder: use userspace pointer as base of buffer space")
Signed-off-by: Todd Kjos <tkjos@google.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20191213202531.55010-1-tkjos@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Todd Kjos 2019-12-13 12:25:31 -08:00 committed by Greg Kroah-Hartman
parent 3e42fe5c73
commit 1698174271
1 changed files with 2 additions and 2 deletions
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4
drivers/android/binder.c
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@ -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,