diff options
| -rw-r--r-- | fs/compat.c | 16 | ||||
| -rw-r--r-- | fs/exec.c | 31 | ||||
| -rw-r--r-- | fs/fs_struct.c | 69 | ||||
| -rw-r--r-- | fs/internal.h | 2 | ||||
| -rw-r--r-- | fs/proc/task_nommu.c | 2 | ||||
| -rw-r--r-- | include/linux/fs_struct.h | 8 | ||||
| -rw-r--r-- | kernel/fork.c | 37 |
7 files changed, 121 insertions, 44 deletions
diff --git a/fs/compat.c b/fs/compat.c index 55efdfe..baabf20 100644 --- a/fs/compat.c +++ b/fs/compat.c @@ -51,6 +51,7 @@ #include <linux/poll.h> #include <linux/mm.h> #include <linux/eventpoll.h> +#include <linux/fs_struct.h> #include <asm/uaccess.h> #include <asm/mmu_context.h> @@ -1441,12 +1442,15 @@ int compat_do_execve(char * filename, bprm->cred = prepare_exec_creds(); if (!bprm->cred) goto out_unlock; - check_unsafe_exec(bprm); + + retval = check_unsafe_exec(bprm); + if (retval) + goto out_unlock; file = open_exec(filename); retval = PTR_ERR(file); if (IS_ERR(file)) - goto out_unlock; + goto out_unmark; sched_exec(); @@ -1488,6 +1492,9 @@ int compat_do_execve(char * filename, goto out; /* execve succeeded */ + write_lock(¤t->fs->lock); + current->fs->in_exec = 0; + write_unlock(¤t->fs->lock); current->in_execve = 0; mutex_unlock(¤t->cred_exec_mutex); acct_update_integrals(current); @@ -1506,6 +1513,11 @@ out_file: fput(bprm->file); } +out_unmark: + write_lock(¤t->fs->lock); + current->fs->in_exec = 0; + write_unlock(¤t->fs->lock); + out_unlock: current->in_execve = 0; mutex_unlock(¤t->cred_exec_mutex); @@ -1056,16 +1056,18 @@ EXPORT_SYMBOL(install_exec_creds); * - the caller must hold current->cred_exec_mutex to protect against * PTRACE_ATTACH */ -void check_unsafe_exec(struct linux_binprm *bprm) +int check_unsafe_exec(struct linux_binprm *bprm) { struct task_struct *p = current, *t; unsigned long flags; unsigned n_fs, n_sighand; + int res = 0; bprm->unsafe = tracehook_unsafe_exec(p); n_fs = 1; n_sighand = 1; + write_lock(&p->fs->lock); lock_task_sighand(p, &flags); for (t = next_thread(p); t != p; t = next_thread(t)) { if (t->fs == p->fs) @@ -1073,11 +1075,19 @@ void check_unsafe_exec(struct linux_binprm *bprm) n_sighand++; } - if (atomic_read(&p->fs->count) > n_fs || - atomic_read(&p->sighand->count) > n_sighand) + if (p->fs->users > n_fs || + atomic_read(&p->sighand->count) > n_sighand) { bprm->unsafe |= LSM_UNSAFE_SHARE; + } else { + if (p->fs->in_exec) + res = -EAGAIN; + p->fs->in_exec = 1; + } unlock_task_sighand(p, &flags); + write_unlock(&p->fs->lock); + + return res; } /* @@ -1296,12 +1306,15 @@ int do_execve(char * filename, bprm->cred = prepare_exec_creds(); if (!bprm->cred) goto out_unlock; - check_unsafe_exec(bprm); + + retval = check_unsafe_exec(bprm); + if (retval) + goto out_unlock; file = open_exec(filename); retval = PTR_ERR(file); if (IS_ERR(file)) - goto out_unlock; + goto out_unmark; sched_exec(); @@ -1344,6 +1357,9 @@ int do_execve(char * filename, goto out; /* execve succeeded */ + write_lock(¤t->fs->lock); + current->fs->in_exec = 0; + write_unlock(¤t->fs->lock); current->in_execve = 0; mutex_unlock(¤t->cred_exec_mutex); acct_update_integrals(current); @@ -1362,6 +1378,11 @@ out_file: fput(bprm->file); } +out_unmark: + write_lock(¤t->fs->lock); + current->fs->in_exec = 0; + write_unlock(¤t->fs->lock); + out_unlock: current->in_execve = 0; mutex_unlock(¤t->cred_exec_mutex); diff --git a/fs/fs_struct.c b/fs/fs_struct.c index 36e0a12..41cff72 100644 --- a/fs/fs_struct.c +++ b/fs/fs_struct.c @@ -72,25 +72,27 @@ void chroot_fs_refs(struct path *old_root, struct path *new_root) path_put(old_root); } -void put_fs_struct(struct fs_struct *fs) +void free_fs_struct(struct fs_struct *fs) { - /* No need to hold fs->lock if we are killing it */ - if (atomic_dec_and_test(&fs->count)) { - path_put(&fs->root); - path_put(&fs->pwd); - kmem_cache_free(fs_cachep, fs); - } + path_put(&fs->root); + path_put(&fs->pwd); + kmem_cache_free(fs_cachep, fs); } void exit_fs(struct task_struct *tsk) { - struct fs_struct * fs = tsk->fs; + struct fs_struct *fs = tsk->fs; if (fs) { + int kill; task_lock(tsk); + write_lock(&fs->lock); tsk->fs = NULL; + kill = !--fs->users; + write_unlock(&fs->lock); task_unlock(tsk); - put_fs_struct(fs); + if (kill) + free_fs_struct(fs); } } @@ -99,7 +101,8 @@ struct fs_struct *copy_fs_struct(struct fs_struct *old) struct fs_struct *fs = kmem_cache_alloc(fs_cachep, GFP_KERNEL); /* We don't need to lock fs - think why ;-) */ if (fs) { - atomic_set(&fs->count, 1); + fs->users = 1; + fs->in_exec = 0; rwlock_init(&fs->lock); fs->umask = old->umask; read_lock(&old->lock); @@ -114,28 +117,54 @@ struct fs_struct *copy_fs_struct(struct fs_struct *old) int unshare_fs_struct(void) { - struct fs_struct *fsp = copy_fs_struct(current->fs); - if (!fsp) + struct fs_struct *fs = current->fs; + struct fs_struct *new_fs = copy_fs_struct(fs); + int kill; + + if (!new_fs) return -ENOMEM; - exit_fs(current); - current->fs = fsp; + + task_lock(current); + write_lock(&fs->lock); + kill = !--fs->users; + current->fs = new_fs; + write_unlock(&fs->lock); + task_unlock(current); + + if (kill) + free_fs_struct(fs); + return 0; } EXPORT_SYMBOL_GPL(unshare_fs_struct); /* to be mentioned only in INIT_TASK */ struct fs_struct init_fs = { - .count = ATOMIC_INIT(1), + .users = 1, .lock = __RW_LOCK_UNLOCKED(init_fs.lock), .umask = 0022, }; void daemonize_fs_struct(void) { - struct fs_struct *fs; + struct fs_struct *fs = current->fs; + + if (fs) { + int kill; + + task_lock(current); - exit_fs(current); /* current->fs->count--; */ - fs = &init_fs; - current->fs = fs; - atomic_inc(&fs->count); + write_lock(&init_fs.lock); + init_fs.users++; + write_unlock(&init_fs.lock); + + write_lock(&fs->lock); + current->fs = &init_fs; + kill = !--fs->users; + write_unlock(&fs->lock); + + task_unlock(current); + if (kill) + free_fs_struct(fs); + } } diff --git a/fs/internal.h b/fs/internal.h index 477a105f..b4dac4f 100644 --- a/fs/internal.h +++ b/fs/internal.h @@ -44,7 +44,7 @@ extern void __init chrdev_init(void); /* * exec.c */ -extern void check_unsafe_exec(struct linux_binprm *); +extern int check_unsafe_exec(struct linux_binprm *); /* * namespace.c diff --git a/fs/proc/task_nommu.c b/fs/proc/task_nommu.c index 343ea12..6ca0105 100644 --- a/fs/proc/task_nommu.c +++ b/fs/proc/task_nommu.c @@ -49,7 +49,7 @@ void task_mem(struct seq_file *m, struct mm_struct *mm) else bytes += kobjsize(mm); - if (current->fs && atomic_read(¤t->fs->count) > 1) + if (current->fs && current->fs->users > 1) sbytes += kobjsize(current->fs); else bytes += kobjsize(current->fs); diff --git a/include/linux/fs_struct.h b/include/linux/fs_struct.h index 298cef1..78a05bf 100644 --- a/include/linux/fs_struct.h +++ b/include/linux/fs_struct.h @@ -4,12 +4,10 @@ #include <linux/path.h> struct fs_struct { - atomic_t count; /* This usage count is used by check_unsafe_exec() for - * security checking purposes - therefore it may not be - * incremented, except by clone(CLONE_FS). - */ + int users; rwlock_t lock; int umask; + int in_exec; struct path root, pwd; }; @@ -19,7 +17,7 @@ extern void exit_fs(struct task_struct *); extern void set_fs_root(struct fs_struct *, struct path *); extern void set_fs_pwd(struct fs_struct *, struct path *); extern struct fs_struct *copy_fs_struct(struct fs_struct *); -extern void put_fs_struct(struct fs_struct *); +extern void free_fs_struct(struct fs_struct *); extern void daemonize_fs_struct(void); extern int unshare_fs_struct(void); diff --git a/kernel/fork.c b/kernel/fork.c index 05c02dc..51f138a 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -683,11 +683,19 @@ fail_nomem: static int copy_fs(unsigned long clone_flags, struct task_struct *tsk) { + struct fs_struct *fs = current->fs; if (clone_flags & CLONE_FS) { - atomic_inc(¤t->fs->count); + /* tsk->fs is already what we want */ + write_lock(&fs->lock); + if (fs->in_exec) { + write_unlock(&fs->lock); + return -EAGAIN; + } + fs->users++; + write_unlock(&fs->lock); return 0; } - tsk->fs = copy_fs_struct(current->fs); + tsk->fs = copy_fs_struct(fs); if (!tsk->fs) return -ENOMEM; return 0; @@ -1518,12 +1526,16 @@ static int unshare_fs(unsigned long unshare_flags, struct fs_struct **new_fsp) { struct fs_struct *fs = current->fs; - if ((unshare_flags & CLONE_FS) && - (fs && atomic_read(&fs->count) > 1)) { - *new_fsp = copy_fs_struct(current->fs); - if (!*new_fsp) - return -ENOMEM; - } + if (!(unshare_flags & CLONE_FS) || !fs) + return 0; + + /* don't need lock here; in the worst case we'll do useless copy */ + if (fs->users == 1) + return 0; + + *new_fsp = copy_fs_struct(fs); + if (!*new_fsp) + return -ENOMEM; return 0; } @@ -1639,8 +1651,13 @@ SYSCALL_DEFINE1(unshare, unsigned long, unshare_flags) if (new_fs) { fs = current->fs; + write_lock(&fs->lock); current->fs = new_fs; - new_fs = fs; + if (--fs->users) + new_fs = NULL; + else + new_fs = fs; + write_unlock(&fs->lock); } if (new_mm) { @@ -1679,7 +1696,7 @@ bad_unshare_cleanup_sigh: bad_unshare_cleanup_fs: if (new_fs) - put_fs_struct(new_fs); + free_fs_struct(new_fs); bad_unshare_cleanup_thread: bad_unshare_out: |
