If "hidepid=4" mount option is set then do not instantiate pids that we can not ptrace. "hidepid=4" means that procfs should only contain pids that the caller can ptrace. Cc: Kees Cook <keescook@xxxxxxxxxxxx> Cc: Andy Lutomirski <luto@xxxxxxxxxx> Signed-off-by: Djalal Harouni <tixxdz@xxxxxxxxx> Signed-off-by: Alexey Gladkov <gladkov.alexey@xxxxxxxxx> --- fs/proc/base.c | 15 +++++++++++++++ fs/proc/root.c | 14 +++++++++++--- include/linux/proc_fs.h | 1 + 3 files changed, 27 insertions(+), 3 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..57276cb65528 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -52,6 +52,15 @@ static const struct fs_parameter_description proc_fs_parameters = { .specs = proc_param_specs, }; +static inline int +valid_hidepid(unsigned int value) +{ + return (value == HIDEPID_OFF || + value == HIDEPID_NO_ACCESS || + value == HIDEPID_INVISIBLE || + value == HIDEPID_NOT_PTRACABLE); +} + static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) { struct proc_fs_context *ctx = fc->fs_private; @@ -68,10 +77,9 @@ static int proc_parse_param(struct fs_context *fc, struct fs_parameter *param) break; case Opt_hidepid: + if (!valid_hidepid(result.uint_32)) + return invalf(fc, "proc: unknown value of hidepid.\n"); 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"); break; default: diff --git a/include/linux/proc_fs.h b/include/linux/proc_fs.h index f307940f8311..6822548405a7 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 = 4, /* Limit pids to only ptracable pids */ }; struct proc_fs_info { -- 2.24.1