[PATCH v6 08/10] proc: instantiate only pids that we can ptrace on 'hidepid=3' mount option
From: Alexey Gladkov <hidden>
Date: 2019-12-25 13:03:50
Also in:
linux-api, linux-fsdevel, lkml
Subsystem:
filesystems (vfs and infrastructure), proc filesystem, the rest · Maintainers:
Alexander Viro, Christian Brauner, Linus Torvalds
If "hidepid=3" mount option is set then do not instantiate pids that we can not ptrace. "hidepid=3" means that procfs should only contain pids that the caller can ptrace. Cc: Kees Cook <redacted> Cc: Andy Lutomirski <luto@kernel.org> Signed-off-by: Djalal Harouni <redacted> Signed-off-by: Alexey Gladkov <redacted> --- fs/proc/base.c | 15 +++++++++++++++ fs/proc/root.c | 4 ++-- include/linux/proc_fs.h | 1 + 3 files changed, 18 insertions(+), 2 deletions(-)
diff --git a/fs/proc/base.c b/fs/proc/base.c
index f4f1bcb28603..b55d205a7f6e 100644
--- a/fs/proc/base.c
+++ b/fs/proc/base.c@@ -699,6 +699,14 @@ static bool has_pid_permissions(struct proc_fs_info *fs_info, struct task_struct *task, int hide_pid_min) { + /* + * If 'hidpid' mount option is set force a ptrace check, + * we indicate that we are using a filesystem syscall + * by passing PTRACE_MODE_READ_FSCREDS + */ + if (proc_fs_hide_pid(fs_info) == HIDEPID_NOT_PTRACABLE) + return ptrace_may_access(task, PTRACE_MODE_READ_FSCREDS); + if (proc_fs_hide_pid(fs_info) < hide_pid_min) return true; if (in_group_p(proc_fs_pid_gid(fs_info)))
@@ -3274,7 +3282,14 @@ struct dentry *proc_pid_lookup(struct dentry *dentry, unsigned int flags) if (!task) goto out; + /* Limit procfs to only ptracable tasks */ + if (proc_fs_hide_pid(fs_info) == HIDEPID_NOT_PTRACABLE) { + if (!has_pid_permissions(fs_info, task, HIDEPID_NO_ACCESS)) + goto out_put_task; + } + result = proc_pid_instantiate(dentry, task, NULL); +out_put_task: put_task_struct(task); out: return result;
diff --git a/fs/proc/root.c b/fs/proc/root.c
index 3bb8df360cf7..3c7b29140293 100644
--- a/fs/proc/root.c
+++ b/fs/proc/root.c@@ -70,8 +70,8 @@ static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) case Opt_hidepid: ctx->hidepid = result.uint_32; if (ctx->hidepid < HIDEPID_OFF || - ctx->hidepid > HIDEPID_INVISIBLE) - return invalf(fc, "proc: hidepid value must be between 0 and 2.\n"); + ctx->hidepid > HIDEPID_NOT_PTRACABLE) + return invalf(fc, "proc: hidepid value must be between 0 and 3.\n"); break; default:
diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h
index e349fcafd729..83c87ea65505 100644
--- a/include/linux/proc_fs.h
+++ b/include/linux/proc_fs.h@@ -17,6 +17,7 @@ enum { HIDEPID_OFF = 0, HIDEPID_NO_ACCESS = 1, HIDEPID_INVISIBLE = 2, + HIDEPID_NOT_PTRACABLE = 3, /* Limit pids to only ptracable pids */ }; struct proc_fs_info {
--
2.24.1