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Message-ID: <20150122024554.GB23762@mail.thefacebook.com>
Date: Wed, 21 Jan 2015 18:45:54 -0800
From: Calvin Owens <calvinowens@...com>
To: Cyrill Gorcunov <gorcunov@...il.com>,
"Kirill A. Shutemov" <kirill@...temov.name>
CC: Andrew Morton <akpm@...ux-foundation.org>,
Alexey Dobriyan <adobriyan@...il.com>,
Oleg Nesterov <oleg@...hat.com>,
"Eric W. Biederman" <ebiederm@...ssion.com>,
Al Viro <viro@...iv.linux.org.uk>,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
Peter Feiner <pfeiner@...gle.com>,
Grant Likely <grant.likely@...retlab.ca>,
Siddhesh Poyarekar <siddhesh.poyarekar@...il.com>,
<linux-kernel@...r.kernel.org>, <kernel-team@...com>,
Pavel Emelyanov <xemul@...nvz.org>
Subject: [RFC][PATCH] procfs: Always expose /proc/<pid>/map_files/ and make
it readable
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 <calvinowens@...com>
---
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
--
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