[PATCH bpf-next v4 0/3] bpf: Fix use-after-free of sockmap

Jiayuan Chen
2025-04-08T07:31:05Z

Syzkaller reported this issue [1].

The current sockmap has a dependency on sk_socket in both read and write
stages, but there is a possibility that sk->sk_socket is released during
the process, leading to panic situations. For a detailed reproduction,
please refer to the description in the v2:
https://lore.kernel.org/bpf/20250228055106.58071-1-jiayuan.chen@linux.dev/

The corresponding fix approaches are described in the commit messages of
each patch.

By the way, the current sockmap lacks statistical information, especially
global statistics, such as the number of successful or failed rx and tx
operations. These statistics cannot be obtained from the socket interface
itself.

These data will be of great help in troubleshooting issues and observing
sockmap behavior.

If the maintainer/reviewer does not object, I think we can provide these
statistical information in the future, either through proc/trace/bpftool.

[1] https://syzkaller.appspot.com/bug?extid=dd90a702f518e0eac072

---
v3 -> v4:
1. Rebase on -rc.
2. Incorporated valuable feedback from the v3 thread into the commit
message, making it easier to review.
https://lore.kernel.org/all/20250317092257.68760-3-jiayuan.chen@linux.dev/

v2 -> v3:
1. Michal Luczaj reported similar race issue under sockmap sending path.
2. Rcu lock is conflict with mutex_lock in unix socket read implementation.
https://lore.kernel.org/bpf/20250228055106.58071-1-jiayuan.chen@linux.dev/

v1 -> v2:
1. Add Fixes tag.
2. Extend selftest of edge case for TCP/UDP sockets.
3. Add Reviewed-by and Acked-by tag.
https://lore.kernel.org/bpf/20250226132242.52663-1-jiayuan.chen@linux.dev/T/#t

Jiayuan Chen (3):
bpf, sockmap: avoid using sk_socket after free when sending
bpf, sockmap: avoid using sk_socket after free when reading
selftests/bpf: Add edge case tests for sockmap

net/core/skmsg.c | 22 ++++++-
.../selftests/bpf/prog_tests/socket_helpers.h | 13 +++-
.../selftests/bpf/prog_tests/sockmap_basic.c | 60 +++++++++++++++++++
3 files changed, 91 insertions(+), 4 deletions(-)

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2.47.1