Merge branch 'bpf-fix-trampoline-image-uaf-on-multi-detach-failure'

Hui Zhu says:

====================
bpf: Fix trampoline image UAF on multi detach failure

From: Hui Zhu <zhuhui@kylinos.cn>

This series fixes a UAF in bpf_trampoline_multi_attach_free() where
old_image is freed while ftrace still calls into it, and makes
bpf_trampoline_multi_detach() return void as suggested by Jiri Olsa.

Patch 1 fixes the UAF.  Patch 2 is an independent cleanup that
changes the return type to void and drops the WARN_ON_ONCE at the
call site.

Changelog:
v5:
According to the comments of bot+bpf-ci, split the single patch into
two: the bug fix and the return-type cleanup.
v4:
According to the comments of bot+bpf-ci, add Fixes: and update comments
of bpf_trampoline_multi_attach_free.
v3:
According to the comments of Jiri Olsa, drop patches 2/3 and the
prog-side machinery.
keep only the simplified image-side fix in
bpf_trampoline_multi_attach_free() and make
bpf_trampoline_multi_detach() return void.
v2:
Folded v1's two detach patches into patch 1.
According to the comments of Jiri Olsa, Pin the prog (pinned_prog) on
cur_image so it stays alive while ftrace may still call into it.
Make bpf_trampoline_multi_detach() return void.
Fix the same UAF in standard (non-multi) trampolines.
According to the comments of sashiko, Fix the prog UAF in
bpf_trampoline_multi_attach() rollback.
Leak the trampoline in bpf_trampoline_put() when cur_image is left
by a rollback.
====================

Link: https://patch.msgid.link/cover.1786412280.git.zhuhui@kylinos.cn
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>

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