diff options
| -rw-r--r-- | Documentation/filesystems/proc.rst | 52 | ||||
| -rw-r--r-- | fs/proc/inode.c | 15 | ||||
| -rw-r--r-- | fs/proc/root.c | 38 | ||||
| -rw-r--r-- | tools/testing/selftests/proc/.gitignore | 1 | ||||
| -rw-r--r-- | tools/testing/selftests/proc/Makefile | 1 | ||||
| -rw-r--r-- | tools/testing/selftests/proc/proc-fsconfig-hidepid.c | 50 |
6 files changed, 126 insertions, 31 deletions
diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst index 360486c7a992..e2ecf248feb5 100644 --- a/Documentation/filesystems/proc.rst +++ b/Documentation/filesystems/proc.rst @@ -2147,28 +2147,28 @@ The following mount options are supported: subset= Show only the specified subset of procfs. ========= ======================================================== -hidepid=0 means classic mode - everybody may access all /proc/<pid>/ directories -(default). - -hidepid=1 means users may not access any /proc/<pid>/ directories but their -own. Sensitive files like cmdline, sched*, status are now protected against -other users. This makes it impossible to learn whether any user runs -specific program (given the program doesn't reveal itself by its behaviour). -As an additional bonus, as /proc/<pid>/cmdline is unaccessible for other users, -poorly written programs passing sensitive information via program arguments are -now protected against local eavesdroppers. - -hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be fully invisible to other -users. It doesn't mean that it hides a fact whether a process with a specific -pid value exists (it can be learned by other means, e.g. by "kill -0 $PID"), -but it hides process' uid and gid, which may be learned by stat()'ing -/proc/<pid>/ otherwise. It greatly complicates an intruder's task of gathering -information about running processes, whether some daemon runs with elevated -privileges, whether other user runs some sensitive program, whether other users -run any program at all, etc. - -hidepid=4 means that procfs should only contain /proc/<pid>/ directories -that the caller can ptrace. +hidepid=off or hidepid=0 means classic mode - everybody may access all +/proc/<pid>/ directories (default). + +hidepid=noaccess or hidepid=1 means users may not access any /proc/<pid>/ +directories but their own. Sensitive files like cmdline, sched*, status are now +protected against other users. This makes it impossible to learn whether any +user runs specific program (given the program doesn't reveal itself by its +behaviour). As an additional bonus, as /proc/<pid>/cmdline is unaccessible for +other users, poorly written programs passing sensitive information via program +arguments are now protected against local eavesdroppers. + +hidepid=invisible or hidepid=2 means hidepid=1 plus all /proc/<pid>/ will be +fully invisible to other users. It doesn't mean that it hides a fact whether a +process with a specific pid value exists (it can be learned by other means, e.g. +by "kill -0 $PID"), but it hides process' uid and gid, which may be learned by +stat()'ing /proc/<pid>/ otherwise. It greatly complicates an intruder's task of +gathering information about running processes, whether some daemon runs with +elevated privileges, whether other user runs some sensitive program, whether +other users run any program at all, etc. + +hidepid=ptraceable or hidepid=4 means that procfs should only contain +/proc/<pid>/ directories that the caller can ptrace. gid= defines a group authorized to learn processes information otherwise prohibited by hidepid=. If you use some daemon like identd which needs to learn @@ -2216,8 +2216,8 @@ creates a new procfs instance. Mount options affect own procfs instance. It means that it became possible to have several procfs instances displaying tasks with different filtering options in one pid namespace. -# mount -o hidepid=2 -t proc proc /proc -# mount -o hidepid=1 -t proc proc /tmp/proc +# mount -o hidepid=invisible -t proc proc /proc +# mount -o hidepid=noaccess -t proc proc /tmp/proc # grep ^proc /proc/mounts -proc /proc proc rw,relatime,hidepid=2 0 0 -proc /tmp/proc proc rw,relatime,hidepid=1 0 0 +proc /proc proc rw,relatime,hidepid=invisible 0 0 +proc /tmp/proc proc rw,relatime,hidepid=noaccess 0 0 diff --git a/fs/proc/inode.c b/fs/proc/inode.c index 0d5e68fa842f..cbacac2e892b 100644 --- a/fs/proc/inode.c +++ b/fs/proc/inode.c @@ -24,6 +24,7 @@ #include <linux/seq_file.h> #include <linux/slab.h> #include <linux/mount.h> +#include <linux/bug.h> #include <linux/uaccess.h> @@ -165,6 +166,18 @@ void proc_invalidate_siblings_dcache(struct hlist_head *inodes, spinlock_t *lock deactivate_super(old_sb); } +static inline const char *hidepid2str(int v) +{ + switch (v) { + case HIDEPID_OFF: return "off"; + case HIDEPID_NO_ACCESS: return "noaccess"; + case HIDEPID_INVISIBLE: return "invisible"; + case HIDEPID_NOT_PTRACEABLE: return "ptraceable"; + } + WARN_ONCE(1, "bad hide_pid value: %d\n", v); + return "unknown"; +} + static int proc_show_options(struct seq_file *seq, struct dentry *root) { struct proc_fs_info *fs_info = proc_sb_info(root->d_sb); @@ -172,7 +185,7 @@ static int proc_show_options(struct seq_file *seq, struct dentry *root) if (!gid_eq(fs_info->pid_gid, GLOBAL_ROOT_GID)) seq_printf(seq, ",gid=%u", from_kgid_munged(&init_user_ns, fs_info->pid_gid)); if (fs_info->hide_pid != HIDEPID_OFF) - seq_printf(seq, ",hidepid=%u", fs_info->hide_pid); + seq_printf(seq, ",hidepid=%s", hidepid2str(fs_info->hide_pid)); if (fs_info->pidonly != PROC_PIDONLY_OFF) seq_printf(seq, ",subset=pid"); diff --git a/fs/proc/root.c b/fs/proc/root.c index baff006a918f..288093261b7f 100644 --- a/fs/proc/root.c +++ b/fs/proc/root.c @@ -45,7 +45,7 @@ enum proc_param { static const struct fs_parameter_spec proc_fs_parameters[] = { fsparam_u32("gid", Opt_gid), - fsparam_u32("hidepid", Opt_hidepid), + fsparam_string("hidepid", Opt_hidepid), fsparam_string("subset", Opt_subset), {} }; @@ -58,6 +58,37 @@ static inline int valid_hidepid(unsigned int value) value == HIDEPID_NOT_PTRACEABLE); } +static int proc_parse_hidepid_param(struct fs_context *fc, struct fs_parameter *param) +{ + struct proc_fs_context *ctx = fc->fs_private; + struct fs_parameter_spec hidepid_u32_spec = fsparam_u32("hidepid", Opt_hidepid); + struct fs_parse_result result; + int base = (unsigned long)hidepid_u32_spec.data; + + if (param->type != fs_value_is_string) + return invalf(fc, "proc: unexpected type of hidepid value\n"); + + if (!kstrtouint(param->string, base, &result.uint_32)) { + if (!valid_hidepid(result.uint_32)) + return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string); + ctx->hidepid = result.uint_32; + return 0; + } + + if (!strcmp(param->string, "off")) + ctx->hidepid = HIDEPID_OFF; + else if (!strcmp(param->string, "noaccess")) + ctx->hidepid = HIDEPID_NO_ACCESS; + else if (!strcmp(param->string, "invisible")) + ctx->hidepid = HIDEPID_INVISIBLE; + else if (!strcmp(param->string, "ptraceable")) + ctx->hidepid = HIDEPID_NOT_PTRACEABLE; + else + return invalf(fc, "proc: unknown value of hidepid - %s\n", param->string); + + return 0; +} + static int proc_parse_subset_param(struct fs_context *fc, char *value) { struct proc_fs_context *ctx = fc->fs_private; @@ -97,9 +128,8 @@ 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 (proc_parse_hidepid_param(fc, param)) + return -EINVAL; break; case Opt_subset: diff --git a/tools/testing/selftests/proc/.gitignore b/tools/testing/selftests/proc/.gitignore index 126901c5d6f4..bed4b5318a86 100644 --- a/tools/testing/selftests/proc/.gitignore +++ b/tools/testing/selftests/proc/.gitignore @@ -2,6 +2,7 @@ /fd-001-lookup /fd-002-posix-eq /fd-003-kthread +/proc-fsconfig-hidepid /proc-loadavg-001 /proc-multiple-procfs /proc-pid-vm diff --git a/tools/testing/selftests/proc/Makefile b/tools/testing/selftests/proc/Makefile index bf22457256be..8be8a03d2973 100644 --- a/tools/testing/selftests/proc/Makefile +++ b/tools/testing/selftests/proc/Makefile @@ -20,5 +20,6 @@ TEST_GEN_PROGS += setns-dcache TEST_GEN_PROGS += setns-sysvipc TEST_GEN_PROGS += thread-self TEST_GEN_PROGS += proc-multiple-procfs +TEST_GEN_PROGS += proc-fsconfig-hidepid include ../lib.mk diff --git a/tools/testing/selftests/proc/proc-fsconfig-hidepid.c b/tools/testing/selftests/proc/proc-fsconfig-hidepid.c new file mode 100644 index 000000000000..b9af8f537185 --- /dev/null +++ b/tools/testing/selftests/proc/proc-fsconfig-hidepid.c @@ -0,0 +1,50 @@ +/* + * Copyright © 2020 Alexey Gladkov <gladkov.alexey@gmail.com> + * + * Permission to use, copy, modify, and distribute this software for any + * purpose with or without fee is hereby granted, provided that the above + * copyright notice and this permission notice appear in all copies. + * + * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES + * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF + * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR + * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES + * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN + * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF + * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. + */ +#include <assert.h> +#include <unistd.h> +#include <stdlib.h> +#include <errno.h> +#include <linux/mount.h> +#include <linux/unistd.h> + +static inline int fsopen(const char *fsname, unsigned int flags) +{ + return syscall(__NR_fsopen, fsname, flags); +} + +static inline int fsconfig(int fd, unsigned int cmd, const char *key, const void *val, int aux) +{ + return syscall(__NR_fsconfig, fd, cmd, key, val, aux); +} + +int main(void) +{ + int fsfd, ret; + int hidepid = 2; + + assert((fsfd = fsopen("proc", 0)) != -1); + + ret = fsconfig(fsfd, FSCONFIG_SET_BINARY, "hidepid", &hidepid, 0); + assert(ret == -1); + assert(errno == EINVAL); + + assert(!fsconfig(fsfd, FSCONFIG_SET_STRING, "hidepid", "2", 0)); + assert(!fsconfig(fsfd, FSCONFIG_SET_STRING, "hidepid", "invisible", 0)); + + assert(!close(fsfd)); + + return 0; +} |