netlink: Zero-initialize writer structures allocated on the stack
ClosedPublic
Actions

Authored by markj on Jan 26 2023, 3:07 PM.

Details

Reviewers

Group Reviewers

Commits

rG2e847957c50c: netlink: Zero-initialize writer structures allocated on the stack
rG2de541757e0a: netlink: Zero-initialize writer structures allocated on the stack
rG7a78ae88659e: netlink: Zero-initialize writer structures allocated on the stack

Summary

The prevailing pattern seems to be to simply initialize all fields to
zero. Without this, it's possible to trigger a branch on uninitialized
memory. Specifically, when testing nw->ignore_limit in
nlmsg_refill_buffer().

Initialize the writer structure in a couple of functions where this is
necessary.

Reported by: KMSAN

Diff Detail

Repository

rG FreeBSD src repository

Lint

Lint Skipped

Unit

Tests Skipped

Build Status

Buildable 49246
Build 46136: arc lint + arc unit

Event Timeline

markj created this revision.Jan 26 2023, 3:07 PM

Herald added subscribers: glebius, imp. · View Herald TranscriptJan 26 2023, 3:07 PM

markj requested review of this revision.Jan 26 2023, 3:07 PM

Harbormaster completed remote builds in B49246: Diff 115784.Jan 26 2023, 3:07 PM

Ack, that's a good one!
My initial approach was to perform zero in the -> init() functions (e.g. nlmsg_get_ns_<mbuf|lbuf|buf>), preferably via explicit field initialisation. Apparently the latter one has failed.
ATM I'm leaning towards doing the explicit bzero() in all init functions, but need to think a bit more about it.
To unblock the fix, let's require the explicit writer initialisation for now.

This revision is now accepted and ready to land.Jan 26 2023, 3:24 PM

Closed by commit rG7a78ae88659e: netlink: Zero-initialize writer structures allocated on the stack (authored by markj). · Explain WhyJan 26 2023, 3:46 PM

This revision was automatically updated to reflect the committed changes.

markj added a commit: rG7a78ae88659e: netlink: Zero-initialize writer structures allocated on the stack.

melifaro added a commit: rG2de541757e0a: netlink: Zero-initialize writer structures allocated on the stack.Feb 18 2023, 11:57 AM

melifaro added a commit: rG2e847957c50c: netlink: Zero-initialize writer structures allocated on the stack.Feb 20 2023, 8:13 PM