From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932557AbeDWVuQ (ORCPT ); Mon, 23 Apr 2018 17:50:16 -0400 Received: from mail-wr0-f196.google.com ([209.85.128.196]:46066 "EHLO mail-wr0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932318AbeDWVuN (ORCPT ); Mon, 23 Apr 2018 17:50:13 -0400 X-Google-Smtp-Source: AIpwx4+6RmEhkwtcW+o4/3YUeF0u4Fg1xpjiAI3Xz5+4u6e6S+rfJivxvlrkXjJwc3DF9sFuBjA+rA== Date: Tue, 24 Apr 2018 00:50:09 +0300 From: Alexey Dobriyan To: akpm@linux-foundation.org Cc: linux-kernel@vger.kernel.org, viro@zeniv.linux.org.uk Subject: [PATCH] proc: restore seekdir("/proc", 256) semantics Message-ID: <20180423215009.GE9043@avx2> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Long time ago "/proc/self" was an honest symlink and all not-PID entries were output before /proc/$PID. To not lose /proc/self in readdir output after it became permanently positive dentry it was stuck before /proc/1. One side effect of the change was that the code d = opendir("/proc"); seekdir(d, 256); stopped pointing to the first PID for applications that want to skip all the crap. Later "/proc/thread-self" was added in the same way. It looks like ps and top aren't seeking over /proc but are simply skipping over so nobody noticed. Restore old behaviour, make seekdir(254) point to /proc/self and seekdir(255) point to /proc/thread-self. Commit in question: commit 021ada7dff22d0d9540ff596cb0f8bb866755ee1 procfs: switch /proc/self away from proc_dir_entry Signed-off-by: Alexey Dobriyan --- fs/proc/base.c | 14 ++++++-------- fs/proc/root.c | 4 ++-- 2 files changed, 8 insertions(+), 10 deletions(-) --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -3230,8 +3230,6 @@ static struct tgid_iter next_tgid(struct pid_namespace *ns, struct tgid_iter ite return iter; } -#define TGID_OFFSET (FIRST_PROCESS_ENTRY + 2) - /* for the /proc/ directory itself, after non-process stuff has been done */ int proc_pid_readdir(struct file *file, struct dir_context *ctx) { @@ -3239,22 +3237,22 @@ int proc_pid_readdir(struct file *file, struct dir_context *ctx) struct pid_namespace *ns = file_inode(file)->i_sb->s_fs_info; loff_t pos = ctx->pos; - if (pos >= PID_MAX_LIMIT + TGID_OFFSET) + if (pos >= PID_MAX_LIMIT + FIRST_PROCESS_ENTRY) return 0; - if (pos == TGID_OFFSET - 2) { + if (pos == FIRST_PROCESS_ENTRY - 2) { struct inode *inode = d_inode(ns->proc_self); if (!dir_emit(ctx, "self", 4, inode->i_ino, DT_LNK)) return 0; ctx->pos = pos = pos + 1; } - if (pos == TGID_OFFSET - 1) { + if (pos == FIRST_PROCESS_ENTRY - 1) { struct inode *inode = d_inode(ns->proc_thread_self); if (!dir_emit(ctx, "thread-self", 11, inode->i_ino, DT_LNK)) return 0; ctx->pos = pos = pos + 1; } - iter.tgid = pos - TGID_OFFSET; + iter.tgid = pos - FIRST_PROCESS_ENTRY; iter.task = NULL; for (iter = next_tgid(ns, iter); iter.task; @@ -3267,14 +3265,14 @@ int proc_pid_readdir(struct file *file, struct dir_context *ctx) continue; len = snprintf(name, sizeof(name), "%u", iter.tgid); - ctx->pos = iter.tgid + TGID_OFFSET; + ctx->pos = iter.tgid + FIRST_PROCESS_ENTRY; if (!proc_fill_cache(file, ctx, name, len, proc_pid_instantiate, iter.task, NULL)) { put_task_struct(iter.task); return 0; } } - ctx->pos = PID_MAX_LIMIT + TGID_OFFSET; + ctx->pos = PID_MAX_LIMIT + FIRST_PROCESS_ENTRY; return 0; } --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -162,11 +162,11 @@ static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentr static int proc_root_readdir(struct file *file, struct dir_context *ctx) { - if (ctx->pos < FIRST_PROCESS_ENTRY) { + if (ctx->pos < FIRST_PROCESS_ENTRY - 2) { int error = proc_readdir(file, ctx); if (unlikely(error <= 0)) return error; - ctx->pos = FIRST_PROCESS_ENTRY; + ctx->pos = FIRST_PROCESS_ENTRY - 2; } return proc_pid_readdir(file, ctx);