CVE-2026-31630

In the Linux kernel, the following vulnerability has been resolved:

rxrpc: proc: size address buffers for %pISpc output

The AF_RXRPC procfs helpers format local and remote socket addresses into

fixed 50-byte stack buffers with "%pISpc".

That is too small for the longest current-tree IPv6-with-port form the

formatter can produce. In lib/vsprintf.c, the compressed IPv6 path uses a

dotted-quad tail not only for v4mapped addresses, but also for ISATAP

addresses via ipv6_addr_is_isatap().

As a result, a case such as

[ffff:ffff:ffff:ffff:0:5efe:255.255.255.255]:65535

is possible with the current formatter. That is 50 visible characters, so

51 bytes including the trailing NUL, which does not fit in the existing

char[50] buffers used by net/rxrpc/proc.c.

Size the buffers from the formatter's maximum textual form and switch the

call sites to scnprintf().

Changes since v1:

- correct the changelog to cite the actual maximum current-tree case

explicitly

- frame the proof around the ISATAP formatting path instead of the earlier

mapped-v4 example