From: Todd Kjos tkjos@google.com

stable inclusion from stable-v4.19.224 commit 7c7064402609aeb6fb11be1b4ec10673ff17b593 category: bugfix bugzilla: https://gitee.com/src-openeuler/kernel/issues/I947U7 CVE: CVE-2021-46935

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=...

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commit cfd0d84ba28c18b531648c9d4a35ecca89ad9901 upstream.

In 4.13, commit 74310e06be4d ("android: binder: Move buffer out of area shared with user space") fixed a kernel structure visibility issue. As part of that patch, sizeof(void *) was used as the buffer size for 0-length data payloads so the driver could detect abusive clients sending 0-length asynchronous transactions to a server by enforcing limits on async_free_size.

Unfortunately, on the "free" side, the accounting of async_free_space did not add the sizeof(void *) back. The result was that up to 8-bytes of async_free_space were leaked on every async transaction of 8-bytes or less. These small transactions are uncommon, so this accounting issue has gone undetected for several years.

The fix is to use "buffer_size" (the allocated buffer size) instead of "size" (the logical buffer size) when updating the async_free_space during the free operation. These are the same except for this corner case of asynchronous transactions with payloads < 8 bytes.

Fixes: 74310e06be4d ("android: binder: Move buffer out of area shared with user space") Signed-off-by: Todd Kjos tkjos@google.com Cc: stable@vger.kernel.org # 4.14+ Link: https://lore.kernel.org/r/20211220190150.2107077-1-tkjos@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org Conflicts: drivers/android/binder_alloc.c Signed-off-by: Li Huafei lihuafei1@huawei.com --- drivers/android/binder_alloc.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/android/binder_alloc.c b/drivers/android/binder_alloc.c index af856205d40a..d866a70cba7b 100644 --- a/drivers/android/binder_alloc.c +++ b/drivers/android/binder_alloc.c @@ -622,7 +622,7 @@ static void binder_free_buf_locked(struct binder_alloc *alloc, BUG_ON(buffer->user_data > alloc->buffer + alloc->buffer_size);

if (buffer->async_transaction) { - alloc->free_async_space += size + sizeof(struct binder_buffer); + alloc->free_async_space += buffer_size + sizeof(struct binder_buffer);

binder_alloc_debug(BINDER_DEBUG_BUFFER_ALLOC_ASYNC, "%d: binder_free_buf size %zd async free %zd\n",