| Message ID | 20211101060419.4682-11-laoar.shao@gmail.com (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | extend task comm from 16 to 24 | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
| bpf/vmtest-bpf-next | fail | VM_Test |
| bpf/vmtest-bpf-next-PR | fail | PR summary |
| bpf/vmtest-bpf | fail | VM_Test |
| bpf/vmtest-bpf-PR | fail | PR summary |
diff --git a/include/linux/sched.h b/include/linux/sched.h index 09ac13e54549..a8822e26653e 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -276,10 +276,11 @@ struct task_group; /* * Define the task command name length as enum, then it can be visible to - * BPF programs. + * BPF programs. The TASK_COMM_LEN_16 is kept for backward-compitability. */ enum { - TASK_COMM_LEN = 16, + TASK_COMM_LEN_16 = 16, + TASK_COMM_LEN = 24, }; extern void scheduler_tick(void);
When I was implementing a new per-cpu kthread cfs_migration, I found the comm of it "cfs_migration/%u" is truncated due to the limitation of TASK_COMM_LEN. For example, the comm of the percpu thread on CPU10~19 are all with the same name "cfs_migration/1", which will confuse the user. This issue is not critical, because we can get the corresponding CPU from the task's Cpus_allowed. But for kthreads correspoinding to other hardware devices, it is not easy to get the detailed device info from task comm, for example, jbd2/nvme0n1p2- xfs-reclaim/sdf We can also shorten the name to work around this problem, but I find there are so many truncated kthreads: rcu_tasks_kthre rcu_tasks_rude_ rcu_tasks_trace poll_mpt3sas0_s ext4-rsv-conver xfs-reclaim/sd{a, b, c, ...} xfs-blockgc/sd{a, b, c, ...} xfs-inodegc/sd{a, b, c, ...} audit_send_repl ecryptfs-kthrea vfio-irqfd-clea jbd2/nvme0n1p2- ... We should improve this problem fundamentally by extending comm size to 24 bytes. task_struct is growing rather regularly by 8 bytes. After this change, the truncated kthreads listed above will be displayed as: rcu_tasks_kthread rcu_tasks_rude_kthread rcu_tasks_trace_kthread poll_mpt3sas0_statu ext4-rsv-conversion xfs-reclaim/sdf1 xfs-blockgc/sdf1 xfs-inodegc/sdf1 audit_send_reply ecryptfs-kthread vfio-irqfd-cleanup jbd2/nvme0n1p2-8 As we have converted all the unsafe copy of task comm to the safe one, this change won't make any trouble to the kernel or the in-tree tools. The safe one and unsafe one of comm copy as follows, Unsafe Safe strlcpy strscpy_pad strncpy strscpy_pad bpf_probe_read_kernel bpf_probe_read_kernel_str bpf_core_read_str bpf_get_current_comm perf_event__prepare_comm prctl(2) Regarding the possible risk it may take to the out-of-tree user tools, if the user tools get the task comm through kernel API like prctl(2), bpf_get_current_comm() and etc, the tools still work well after this change. While If the user tools get the task comm through direct string copy, it must make sure the copied string should be with a nul terminator. Signed-off-by: Yafang Shao <laoar.shao@gmail.com> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Arnaldo Carvalho de Melo <arnaldo.melo@gmail.com> Cc: Alexei Starovoitov <alexei.starovoitov@gmail.com> Cc: Andrii Nakryiko <andrii.nakryiko@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Al Viro <viro@zeniv.linux.org.uk> Cc: Kees Cook <keescook@chromium.org> Cc: Petr Mladek <pmladek@suse.com> --- include/linux/sched.h | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-)