kernel/linux
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ synced 2026-11-13 07:31:07 +00:00
Code Issues Releases Packages Activity

Merge branch 'net-a-sockopt_t-quirk-for-the-options-that-write-past-optlen'

Browse source 
Breno Leitao says:

====================
net: a sockopt_t quirk for the options that write past optlen

This series continues the migration of our protocols to sockopt_t, as
described in [1].

There are some protocols that use optlen as the header size, and the real
buffer size comes from a field inside the header. This means a bug, given
that optlen should be the full buffer size, but there are indications [2]
that we have programs that use the bad behaviour above, and we want to
avoid breaking them (or, honestly, avoid being cursed by Linus).

That said, create a quirk helper that preserves the same behaviour, even
using sockopt_t. The way to do it is simple:

1) Only do it for userspace callers (ubuf), otherwise a bug here will
   corrupt the kernel instead of a simple SIGSEGV.
2) Expand optval mid-air based on the header field.

IP_MSFILTER is the first user, and the smallest one: a single caller, no
compat variant, and a reply written front to back. MCAST_MSFILTER on ipv4
and ipv6 comes next, and TCP_AO_GET_KEYS has the same shape. Do this
quirk on IP_MSFILTER to make sure the dynamic is ok, so, we can expand
it later.

None of this is meant to change what userspace sees.
====================

Link: https://patch.msgid.link/20260914-getsockopt_phase6-v2-0-e48befc9602e@debian.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2026-09-18 16:42:47 -07:00
commit 83f09b3bcc
5 changed files with 59 additions and 13 deletions
Download patch file Download diff file Expand all files Collapse all files