title: binder: fix async_free_space accounting for empty parcels
description: In the Linux kernel, the following vulnerability has been resolved:
binder: fix async_free_space accounting for empty parcels
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.
affected:
{
product: Linux
vendor: Linux
defaultStatus: unaffected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions:
version: 74310e06be4d, lessThan: 2d2df539d052, status: affected, versionType: git
version: 74310e06be4d, lessThan: 7c7064402609, status: affected, versionType: git
version: 74310e06be4d, lessThan: 103b16a8c51f, status: affected, versionType: git
version: 74310e06be4d, lessThan: 1cb8444f3114, status: affected, versionType: git
version: 74310e06be4d, lessThan: 17691bada6b2, status: affected, versionType: git
version: 74310e06be4d, lessThan: cfd0d84ba28c, status: affected, versionType: git
}
{
product: Linux
vendor: Linux
defaultStatus: affected
repo: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
versions:
version: 4.14, status: affected
version: 0, lessThan: 4.14, status: unaffected, versionType: custom
version: 4.14.261, lessThanOrEqual: 4.14.*, status: unaffected, versionType: custom
version: 4.19.224, lessThanOrEqual: 4.19.*, status: unaffected, versionType: custom
version: 5.4.170, lessThanOrEqual: 5.4.*, status: unaffected, versionType: custom
version: 5.10.90, lessThanOrEqual: 5.10.*, status: unaffected, versionType: custom
version: 5.15.13, lessThanOrEqual: 5.15.*, status: unaffected, versionType: custom
version: 5.16, lessThanOrEqual: *, status: unaffected, versionType: original_commit_for_fix
}
