On Thu, Feb 24, 2022 at 1:49 PM Yucong Sun <fallentree@xxxxxx> wrote: > > In a previous commit (1), BPF preload process was switched from user > mode process to use in-kernel light skeleton instead. However, in the > kernel context the available fd starts from 0, instead of normally 3 for > user mode process. and the preload process leaked two FDs, taking over > FD 0 and 1. This which later caused issues when kernel trys to setup > stdin/stdout/stderr for init process, assuming fd 0,1,2 is available. > > As seen here: > > Before fix: > ls -lah /proc/1/fd/* > > lrwx------1 root root 64 Feb 23 17:20 /proc/1/fd/0 -> /dev/null > lrwx------ 1 root root 64 Feb 23 17:20 /proc/1/fd/1 -> /dev/null > lrwx------ 1 root root 64 Feb 23 17:20 /proc/1/fd/2 -> /dev/console > lrwx------ 1 root root 64 Feb 23 17:20 /proc/1/fd/6 -> /dev/console > lrwx------ 1 root root 64 Feb 23 17:20 /proc/1/fd/7 -> /dev/console > > After Fix / Normal: > > ls -lah /proc/1/fd/* > > lrwx------ 1 root root 64 Feb 24 21:23 /proc/1/fd/0 -> /dev/console > lrwx------ 1 root root 64 Feb 24 21:23 /proc/1/fd/1 -> /dev/console > lrwx------ 1 root root 64 Feb 24 21:23 /proc/1/fd/2 -> /dev/console > > In this patch: > - skel_closenz was changed to skel_closenez to correctly handle > FD=0 case. > - various places detecting FD > 0 was changed to FD >= 0. > - Call iterators_skel__detach() funciton to release FDs after links > are obtained. > > 1: https://github.com/kernel-patches/bpf/commit/cb80ddc67152e72f28ff6ea8517acdf875d7381d We can just refer to the commit ID as commit cb80ddc67152 ("bpf: Convert bpf_preload.ko to use light skeleton.") And I think we need a Fixes tag for it. Fixes: commit cb80ddc67152 ("bpf: Convert bpf_preload.ko to use light skeleton.") > Signed-off-by: Yucong Sun <fallentree@xxxxxx> Other than these. Acked-by: Song Liu <songliubraving@xxxxxx>
