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Tue, 19 Jun 2018 03:35:05 +0000 Date: Mon, 18 Jun 2018 20:34:51 -0700 From: Andrei Vagin To: David Howells Cc: viro@zeniv.linux.org.uk, linux-nfs@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-afs@lists.infradead.org Subject: Re: [12/24] proc: Add fs_context support to procfs [ver #7] Message-ID: <20180619033450.GA11639@outlook.office365.com> References: <152414474815.23902.6952548431423168966.stgit@warthog.procyon.org.uk> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="82I3+IH0IqGh5yIs" Content-Disposition: inline In-Reply-To: <152414474815.23902.6952548431423168966.stgit@warthog.procyon.org.uk> User-Agent: Mutt/1.9.3 (2018-01-21) X-Originating-IP: [73.140.212.29] X-ClientProxiedBy: MWHPR17CA0065.namprd17.prod.outlook.com (2603:10b6:300:93::27) To AM6PR08MB3253.eurprd08.prod.outlook.com (2603:10a6:209:47::18) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: 1b190068-5242-4d16-5648-08d5d595a6c1 X-Microsoft-Antispam: UriScan:;BCL:0;PCL:0;RULEID:(7020095)(4652020)(4534165)(4627221)(201703031133081)(201702281549075)(5600026)(711020)(2017052603328)(7153060)(49563074)(7193020);SRVR:AM6PR08MB3253; 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charset=koi8-r Content-Disposition: inline Hi David, We run CRIU tests for vfs/for-next, and today a few of these test failed. I found that the problem appears after this patch.. https://travis-ci.org/avagin/linux/jobs/393766778 The reproducer is attached. It creates a process in a new set of namespaces (user, mount, etc) and then this process fails to mount procfs, the mount syscall returns EBUSY. 666 pipe([3, 4]) = 0 666 clone(child_stack=0x7ffc23a89400, flags=CLONE_NEWNS|CLONE_NEWUTS|CLONE_NEWIPC|CLONE_NEWUSER|CLONE_NEWPID|CLONE_NEWNET|SIGCHLD) = 667 666 openat(AT_FDCWD, "/proc/667/uid_map", O_WRONLY 667 close(4 666 <... openat resumed> ) = 5 666 write(5, "0 100000 100000\n100000 200000 50"..., 36 667 <... close resumed> ) = 0 666 <... write resumed> ) = 36 666 close(5 667 read(3, 666 <... close resumed> ) = 0 666 openat(AT_FDCWD, "/proc/667/gid_map", O_WRONLY) = 5 666 write(5, "0 400000 50000\n50000 500000 1000"..., 35) = 35 666 close(5) = 0 666 write(4, " \225\250#", 4) = 4 667 <... read resumed> " \225\250#", 4) = 4 666 wait4(667, 667 setsid() = 1 667 setuid(0) = 0 667 setgid(0) = 0 667 setgroups(0, NULL) = 0 667 mount("proc", "/mnt", "proc", MS_MGC_VAL|MS_NOSUID|MS_NODEV|MS_NOEXEC, NULL) = -1 EBUSY (Device or resource busy) Thanks, Andrei On Thu, Apr 19, 2018 at 02:32:28PM +0100, David Howells wrote: > Add fs_context support to procfs. > > Signed-off-by: David Howells > --- > > fs/proc/inode.c | 2 - > fs/proc/internal.h | 2 - > fs/proc/root.c | 169 ++++++++++++++++++++++++++++++++++------------------ > 3 files changed, 113 insertions(+), 60 deletions(-) > > diff --git a/fs/proc/inode.c b/fs/proc/inode.c > index 0b13cf6eb6d7..7aa86dd65ba8 100644 > --- a/fs/proc/inode.c > +++ b/fs/proc/inode.c > @@ -128,7 +128,7 @@ const struct super_operations proc_sops = { > .drop_inode = generic_delete_inode, > .evict_inode = proc_evict_inode, > .statfs = simple_statfs, > - .remount_fs = proc_remount, > + .reconfigure = proc_reconfigure, > .show_options = proc_show_options, > }; > > diff --git a/fs/proc/internal.h b/fs/proc/internal.h > index 3182e1b636d3..a5ab9504768a 100644 > --- a/fs/proc/internal.h > +++ b/fs/proc/internal.h > @@ -254,7 +254,7 @@ static inline void proc_tty_init(void) {} > extern struct proc_dir_entry proc_root; > > extern void proc_self_init(void); > -extern int proc_remount(struct super_block *, int *, char *, size_t); > +extern int proc_reconfigure(struct super_block *, struct fs_context *); > > /* > * task_[no]mmu.c > diff --git a/fs/proc/root.c b/fs/proc/root.c > index 2fbc177f37a8..e6bd31fbc714 100644 > --- a/fs/proc/root.c > +++ b/fs/proc/root.c > @@ -19,14 +19,24 @@ > #include > #include > #include > +#include > #include > #include > #include > #include > #include > +#include > > #include "internal.h" > > +struct proc_fs_context { > + struct fs_context fc; > + struct pid_namespace *pid_ns; > + unsigned long mask; > + int hidepid; > + int gid; > +}; > + > enum { > Opt_gid, Opt_hidepid, Opt_err, > }; > @@ -37,56 +47,60 @@ static const match_table_t tokens = { > {Opt_err, NULL}, > }; > > -static int proc_parse_options(char *options, struct pid_namespace *pid) > +static int proc_parse_option(struct fs_context *fc, char *opt, size_t len) > { > - char *p; > + struct proc_fs_context *ctx = container_of(fc, struct proc_fs_context, fc); > substring_t args[MAX_OPT_ARGS]; > - int option; > - > - if (!options) > - return 1; > - > - while ((p = strsep(&options, ",")) != NULL) { > - int token; > - if (!*p) > - continue; > - > - args[0].to = args[0].from = NULL; > - token = match_token(p, tokens, args); > - switch (token) { > - case Opt_gid: > - if (match_int(&args[0], &option)) > - return 0; > - pid->pid_gid = make_kgid(current_user_ns(), option); > - break; > - case Opt_hidepid: > - if (match_int(&args[0], &option)) > - return 0; > - if (option < HIDEPID_OFF || > - option > HIDEPID_INVISIBLE) { > - pr_err("proc: hidepid value must be between 0 and 2.\n"); > - return 0; > - } > - pid->hide_pid = option; > - break; > - default: > - pr_err("proc: unrecognized mount option \"%s\" " > - "or missing value\n", p); > - return 0; > + int token; > + > + args[0].to = args[0].from = NULL; > + token = match_token(opt, tokens, args); > + switch (token) { > + case Opt_gid: > + if (match_int(&args[0], &ctx->gid)) > + return -EINVAL; > + break; > + > + case Opt_hidepid: > + if (match_int(&args[0], &ctx->hidepid)) > + return -EINVAL; > + if (ctx->hidepid < HIDEPID_OFF || > + ctx->hidepid > HIDEPID_INVISIBLE) { > + pr_err("proc: hidepid value must be between 0 and 2.\n"); > + return -EINVAL; > } > + break; > + > + default: > + pr_err("proc: unrecognized mount option \"%s\" or missing value\n", > + opt); > + return -EINVAL; > } > > - return 1; > + ctx->mask |= 1 << token; > + return 0; > +} > + > +static void proc_set_options(struct super_block *s, > + struct fs_context *fc, > + struct pid_namespace *pid_ns, > + struct user_namespace *user_ns) > +{ > + struct proc_fs_context *ctx = container_of(fc, struct proc_fs_context, fc); > + > + if (ctx->mask & (1 << Opt_gid)) > + pid_ns->pid_gid = make_kgid(user_ns, ctx->gid); > + if (ctx->mask & (1 << Opt_hidepid)) > + pid_ns->hide_pid = ctx->hidepid; > } > > -static int proc_fill_super(struct super_block *s, void *data, size_t data_size, int silent) > +static int proc_fill_super(struct super_block *s, struct fs_context *fc) > { > - struct pid_namespace *ns = get_pid_ns(s->s_fs_info); > + struct pid_namespace *pid_ns = get_pid_ns(s->s_fs_info); > struct inode *root_inode; > int ret; > > - if (!proc_parse_options(data, ns)) > - return -EINVAL; > + proc_set_options(s, fc, pid_ns, current_user_ns()); > > /* User space would break if executables or devices appear on proc */ > s->s_iflags |= SB_I_USERNS_VISIBLE | SB_I_NOEXEC | SB_I_NODEV; > @@ -103,7 +117,7 @@ static int proc_fill_super(struct super_block *s, void *data, size_t data_size, > * top of it > */ > s->s_stack_depth = FILESYSTEM_MAX_STACK_DEPTH; > - > + > pde_get(&proc_root); > root_inode = proc_get_inode(s, &proc_root); > if (!root_inode) { > @@ -124,30 +138,46 @@ static int proc_fill_super(struct super_block *s, void *data, size_t data_size, > return proc_setup_thread_self(s); > } > > -int proc_remount(struct super_block *sb, int *flags, > - char *data, size_t data_size) > +int proc_reconfigure(struct super_block *sb, struct fs_context *fc) > { > struct pid_namespace *pid = sb->s_fs_info; > > sync_filesystem(sb); > - return !proc_parse_options(data, pid); > + > + if (fc) > + proc_set_options(sb, fc, pid, current_user_ns()); > + return 0; > } > > -static struct dentry *proc_mount(struct file_system_type *fs_type, > - int flags, const char *dev_name, > - void *data, size_t data_size) > +static int proc_get_tree(struct fs_context *fc) > { > - struct pid_namespace *ns; > + struct proc_fs_context *ctx = container_of(fc, struct proc_fs_context, fc); > > - if (flags & SB_KERNMOUNT) { > - ns = data; > - data = NULL; > - } else { > - ns = task_active_pid_ns(current); > - } > + ctx->fc.s_fs_info = ctx->pid_ns; > + return vfs_get_super(fc, vfs_get_keyed_super, proc_fill_super); > +} > > - return mount_ns(fs_type, flags, data, data_size, ns, ns->user_ns, > - proc_fill_super); > +static void proc_fs_context_free(struct fs_context *fc) > +{ > + struct proc_fs_context *ctx = container_of(fc, struct proc_fs_context, fc); > + > + if (ctx->pid_ns) > + put_pid_ns(ctx->pid_ns); > +} > + > +static const struct fs_context_operations proc_fs_context_ops = { > + .free = proc_fs_context_free, > + .parse_option = proc_parse_option, > + .get_tree = proc_get_tree, > +}; > + > +static int proc_init_fs_context(struct fs_context *fc, struct super_block *src_sb) > +{ > + struct proc_fs_context *ctx = container_of(fc, struct proc_fs_context, fc); > + > + ctx->pid_ns = get_pid_ns(task_active_pid_ns(current)); > + ctx->fc.ops = &proc_fs_context_ops; > + return 0; > } > > static void proc_kill_sb(struct super_block *sb) > @@ -165,7 +195,8 @@ static void proc_kill_sb(struct super_block *sb) > > static struct file_system_type proc_fs_type = { > .name = "proc", > - .mount = proc_mount, > + .fs_context_size = sizeof(struct proc_fs_context), > + .init_fs_context = proc_init_fs_context, > .kill_sb = proc_kill_sb, > .fs_flags = FS_USERNS_MOUNT, > }; > @@ -205,7 +236,7 @@ static struct dentry *proc_root_lookup(struct inode * dir, struct dentry * dentr > { > if (!proc_pid_lookup(dir, dentry, flags)) > return NULL; > - > + > return proc_lookup(dir, dentry, flags); > } > > @@ -259,9 +290,31 @@ struct proc_dir_entry proc_root = { > > int pid_ns_prepare_proc(struct pid_namespace *ns) > { > + struct proc_fs_context *ctx; > + struct fs_context *fc; > struct vfsmount *mnt; > + int ret; > + > + fc = vfs_new_fs_context(&proc_fs_type, NULL, 0, > + FS_CONTEXT_FOR_KERNEL_MOUNT); > + if (IS_ERR(fc)) > + return PTR_ERR(fc); > + > + ctx = container_of(fc, struct proc_fs_context, fc); > + if (ctx->pid_ns != ns) { > + put_pid_ns(ctx->pid_ns); > + get_pid_ns(ns); > + ctx->pid_ns = ns; > + } > + > + ret = vfs_get_tree(fc); > + if (ret < 0) { > + put_fs_context(fc); > + return ret; > + } > > - mnt = kern_mount_data(&proc_fs_type, ns, 0); > + mnt = vfs_create_mount(fc); > + put_fs_context(fc); > if (IS_ERR(mnt)) > return PTR_ERR(mnt); > --82I3+IH0IqGh5yIs Content-Type: text/plain; charset=koi8-r Content-Disposition: attachment; filename="test.c" #define _GNU_SOURCE #include #include #include #include #include #include #include #include #include #include #include #define NS_STACK_SIZE 4096 #define __stack_aligned__ __attribute__((aligned(16))) /* All arguments should be above stack, because it grows down */ struct ns_exec_args { char stack[NS_STACK_SIZE] __stack_aligned__; char stack_ptr[0]; int pfd[2]; }; static int ns_exec(void *_arg) { struct ns_exec_args *args = (struct ns_exec_args *) _arg; int ret; close(args->pfd[1]); if (read(args->pfd[0], &ret, sizeof(ret)) != sizeof(ret)) return -1; setsid(); if (setuid(0) || setgid(0) || setgroups(0, NULL)) { fprintf(stderr, "set*id failed: %m\n"); return -1; } if (mount("proc", "/mnt", "proc", MS_MGC_VAL | MS_NOSUID | MS_NOEXEC | MS_NODEV, NULL)) { fprintf(stderr, "mount(/proc) failed: %m\n"); return -1; } return 0; } #define UID_MAP "0 100000 100000\n100000 200000 50000" #define GID_MAP "0 400000 50000\n50000 500000 100000" int main() { pid_t pid; int ret, status; struct ns_exec_args args; int flags; char pname[PATH_MAX]; int fd, pfd[2]; if (pipe(pfd)) return 1; args.pfd[0] = pfd[0]; args.pfd[1] = pfd[1]; flags = CLONE_NEWPID | CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWNET | CLONE_NEWIPC | CLONE_NEWUSER | SIGCHLD; pid = clone(ns_exec, args.stack_ptr, flags, &args); if (pid < 0) { fprintf(stderr, "clone() failed: %m\n"); exit(1); } snprintf(pname, sizeof(pname), "/proc/%d/uid_map", pid); fd = open(pname, O_WRONLY); if (fd < 0) { fprintf(stderr, "open(%s): %m\n", pname); exit(1); } if (write(fd, UID_MAP, sizeof(UID_MAP)) < 0) { fprintf(stderr, "write(" UID_MAP "): %m\n"); exit(1); } close(fd); snprintf(pname, sizeof(pname), "/proc/%d/gid_map", pid); fd = open(pname, O_WRONLY); if (fd < 0) { fprintf(stderr, "open(%s): %m\n", pname); exit(1); } if (write(fd, GID_MAP, sizeof(GID_MAP)) < 0) { fprintf(stderr, "write(" GID_MAP "): %m\n"); exit(1); } close(fd); if (write(pfd[1], &ret, sizeof(ret)) != sizeof(ret)) return 1; if (waitpid(pid, &status, 0) != pid) return 1; if (status) return 1; return 0; } --82I3+IH0IqGh5yIs--