Currently, /proc/<pid>/map_files/ is restricted to CAP_SYS_ADMIN, and is only exposed if CONFIG_CHECKPOINT_RESTORE is set. This interface is very useful for enumerating the files mapped into a process when the more verbose information in /proc/<pid>/maps is not needed.
This patch moves the folder out from behind CHECKPOINT_RESTORE, and removes the CAP_SYS_ADMIN restrictions. To avoid exposing files to processes for whom they may not be visible, a follow_link() stub is added to the inode_operations struct attached to the symlinks that prevent them from being followed without CAP_SYS_ADMIN. Signed-off-by: Calvin Owens <[email protected]> --- fs/proc/base.c | 42 +++++++++++++++++++++++------------------- 1 file changed, 23 insertions(+), 19 deletions(-) diff --git a/fs/proc/base.c b/fs/proc/base.c index 3f3d7ae..7d48003 100644 --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -1632,8 +1632,6 @@ end_instantiate: return dir_emit(ctx, name, len, 1, DT_UNKNOWN); } -#ifdef CONFIG_CHECKPOINT_RESTORE - /* * dname_to_vma_addr - maps a dentry name into two unsigned longs * which represent vma start and end addresses. @@ -1660,11 +1658,6 @@ static int map_files_d_revalidate(struct dentry *dentry, unsigned int flags) if (flags & LOOKUP_RCU) return -ECHILD; - if (!capable(CAP_SYS_ADMIN)) { - status = -EPERM; - goto out_notask; - } - inode = dentry->d_inode; task = get_proc_task(inode); if (!task) @@ -1753,6 +1746,28 @@ struct map_files_info { unsigned char name[4*sizeof(long)+2]; /* max: %lx-%lx\0 */ }; +/* + * Allowing any user to follow the symlinks in /proc/<pid>/map_files/ could + * allow processes to access files that should not be visible to them, so + * restrict follow_link() to CAP_SYS_ADMIN for these files. + */ +static void *proc_map_files_follow_link(struct dentry *d, struct nameidata *n) +{ + if (!capable(CAP_SYS_ADMIN)) + return ERR_PTR(-EPERM); + + return proc_pid_follow_link(d, n); +} + +/* + * Identical to proc_pid_link_inode_operations except for follow_link() + */ +static const struct inode_operations proc_map_files_link_inode_operations = { + .readlink = proc_pid_readlink, + .follow_link = proc_map_files_follow_link, + .setattr = proc_setattr, +}; + static int proc_map_files_instantiate(struct inode *dir, struct dentry *dentry, struct task_struct *task, const void *ptr) @@ -1768,7 +1783,7 @@ proc_map_files_instantiate(struct inode *dir, struct dentry *dentry, ei = PROC_I(inode); ei->op.proc_get_link = proc_map_files_get_link; - inode->i_op = &proc_pid_link_inode_operations; + inode->i_op = &proc_map_files_link_inode_operations; inode->i_size = 64; inode->i_mode = S_IFLNK; @@ -1792,10 +1807,6 @@ static struct dentry *proc_map_files_lookup(struct inode *dir, int result; struct mm_struct *mm; - result = -EPERM; - if (!capable(CAP_SYS_ADMIN)) - goto out; - result = -ENOENT; task = get_proc_task(dir); if (!task) @@ -1849,10 +1860,6 @@ proc_map_files_readdir(struct file *file, struct dir_context *ctx) struct map_files_info *p; int ret; - ret = -EPERM; - if (!capable(CAP_SYS_ADMIN)) - goto out; - ret = -ENOENT; task = get_proc_task(file_inode(file)); if (!task) @@ -2040,7 +2047,6 @@ static const struct file_operations proc_timers_operations = { .llseek = seq_lseek, .release = seq_release_private, }; -#endif /* CONFIG_CHECKPOINT_RESTORE */ static int proc_pident_instantiate(struct inode *dir, struct dentry *dentry, struct task_struct *task, const void *ptr) @@ -2537,9 +2543,7 @@ static const struct inode_operations proc_task_inode_operations; static const struct pid_entry tgid_base_stuff[] = { DIR("task", S_IRUGO|S_IXUGO, proc_task_inode_operations, proc_task_operations), DIR("fd", S_IRUSR|S_IXUSR, proc_fd_inode_operations, proc_fd_operations), -#ifdef CONFIG_CHECKPOINT_RESTORE DIR("map_files", S_IRUSR|S_IXUSR, proc_map_files_inode_operations, proc_map_files_operations), -#endif DIR("fdinfo", S_IRUSR|S_IXUSR, proc_fdinfo_inode_operations, proc_fdinfo_operations), DIR("ns", S_IRUSR|S_IXUGO, proc_ns_dir_inode_operations, proc_ns_dir_operations), #ifdef CONFIG_NET -- 2.1.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
