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binder: check for overflow when alloc for security context 

When allocating space in the target buffer for the security context,
make sure the extra_buffers_size doesn't overflow. This can only
happen if the given size is invalid, but an overflow can turn it
into a valid size. Fail the transaction if an overflow is detected.

Signed-off-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Todd Kjos 2019-04-24 12:31:18 -07:00 committed by Greg Kroah-Hartman
parent d2f4a83fe3
commit 0b0509508b
1 changed files with 11 additions and 1 deletions
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12
drivers/android/binder.c
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@ -3121,6 +3121,7 @@ static void binder_transaction(struct binder_proc *proc,
if (target_node && target_node->txn_security_ctx) {
u32 secid;
size_t added_size;
security_task_getsecid(proc->tsk, &secid);
ret = security_secid_to_secctx(secid, &secctx, &secctx_sz);
@ -3130,7 +3131,15 @@ static void binder_transaction(struct binder_proc *proc,
return_error_line = __LINE__;
goto err_get_secctx_failed;
}
extra_buffers_size += ALIGN(secctx_sz, sizeof(u64));
added_size = ALIGN(secctx_sz, sizeof(u64));
extra_buffers_size += added_size;
if (extra_buffers_size < added_size) {
/* integer overflow of extra_buffers_size */
return_error = BR_FAILED_REPLY;
return_error_param = EINVAL;
return_error_line = __LINE__;
goto err_bad_extra_size;
}
}
trace_binder_transaction(reply, t, target_node);
@ -3480,6 +3489,7 @@ err_copy_data_failed:
t->buffer->transaction = NULL;
binder_alloc_free_buf(&target_proc->alloc, t->buffer);
err_binder_alloc_buf_failed:
err_bad_extra_size:
if (secctx)
security_release_secctx(secctx, secctx_sz);
err_get_secctx_failed: