CVE-2021-46935

Summary

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 Software

VendorProductVersion RangeStatus
LinuxLinux74310e06be4d74dcf67cd108366710dee5c576d5 < 2d2df539d05205fd83c404d5f2dff48d36f9b495affected
LinuxLinux74310e06be4d74dcf67cd108366710dee5c576d5 < 7c7064402609aeb6fb11be1b4ec10673ff17b593affected
LinuxLinux74310e06be4d74dcf67cd108366710dee5c576d5 < 103b16a8c51f96d5fe063022869ea906c256e5daaffected
LinuxLinux74310e06be4d74dcf67cd108366710dee5c576d5 < 1cb8444f3114f0bb2f6e3bcadcf09aa4a28425d4affected
LinuxLinux74310e06be4d74dcf67cd108366710dee5c576d5 < 17691bada6b2f1d5f1c0f6d28cd9d0727023b0ffaffected
LinuxLinux74310e06be4d74dcf67cd108366710dee5c576d5 < cfd0d84ba28c18b531648c9d4a35ecca89ad9901affected
LinuxLinux4.14affected
LinuxLinux0 < 4.14unaffected
LinuxLinux4.14.261 <= 4.14.*unaffected
LinuxLinux4.19.224 <= 4.19.*unaffected
LinuxLinux5.4.170 <= 5.4.*unaffected
LinuxLinux5.10.90 <= 5.10.*unaffected
LinuxLinux5.15.13 <= 5.15.*unaffected
LinuxLinux5.16 <= *unaffected

Weaknesses

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

CVE Program Container

Additional References

References