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Subject[PATCH 1/1] fs: inotify: Add full paths option to inotify
Date
Adds a flag IN_FULL_PATHS which causes inotify
to return the full path instead of only a filename.

Includes a permissions check on IN_MOVE_SELF to prevent
exposing paths if the user does not have permission to view
the new path.

Signed-off-by: Oliver Ford <ojford@gmail.com>
---
fs/notify/inotify/inotify_fsnotify.c | 55 ++++++++++++++++++++++------
fs/notify/inotify/inotify_user.c | 19 +++++++++-
include/linux/inotify.h | 2 +-
include/uapi/linux/inotify.h | 1 +
4 files changed, 63 insertions(+), 14 deletions(-)

diff --git a/fs/notify/inotify/inotify_fsnotify.c b/fs/notify/inotify/inotify_fsnotify.c
index 49cfe2ae6d23..6334d1d6d5f5 100644
--- a/fs/notify/inotify/inotify_fsnotify.c
+++ b/fs/notify/inotify/inotify_fsnotify.c
@@ -64,12 +64,39 @@ int inotify_handle_inode_event(struct fsnotify_mark *inode_mark, u32 mask,
struct inotify_event_info *event;
struct fsnotify_event *fsn_event;
struct fsnotify_group *group = inode_mark->group;
+ struct dentry *en = NULL;
int ret;
int len = 0;
int alloc_len = sizeof(struct inotify_event_info);
struct mem_cgroup *old_memcg;
-
- if (name) {
+ char *path_buf, *path_bufp = NULL;
+ bool found_full_path = false;
+
+ if (inode_mark->mask & IN_FULL_PATHS && inode) {
+ mask |= IN_FULL_PATHS;
+ en = d_find_any_alias(inode);
+ if (en)
+ found_full_path = true;
+ else if (dir)
+ en = d_find_any_alias(dir);
+
+ if (en) {
+ path_buf = kmalloc(PATH_MAX, GFP_KERNEL);
+ if (unlikely(!path_buf))
+ goto oom;
+
+ path_bufp = dentry_path_raw(en, path_buf, PATH_MAX);
+ len = strlen(path_bufp);
+ alloc_len += len + 1;
+
+ if (!found_full_path) {
+ *(path_bufp + len) = '/';
+ strcat(path_bufp + len + 1, name->name);
+ len += name->len + 1;
+ alloc_len += name->len + 1;
+ }
+ }
+ } else if (name) {
len = name->len;
alloc_len += len + 1;
}
@@ -89,14 +116,8 @@ int inotify_handle_inode_event(struct fsnotify_mark *inode_mark, u32 mask,
event = kmalloc(alloc_len, GFP_KERNEL_ACCOUNT | __GFP_RETRY_MAYFAIL);
set_active_memcg(old_memcg);

- if (unlikely(!event)) {
- /*
- * Treat lost event due to ENOMEM the same way as queue
- * overflow to let userspace know event was lost.
- */
- fsnotify_queue_overflow(group);
- return -ENOMEM;
- }
+ if (unlikely(!event))
+ goto oom;

/*
* We now report FS_ISDIR flag with MOVE_SELF and DELETE_SELF events
@@ -113,8 +134,13 @@ int inotify_handle_inode_event(struct fsnotify_mark *inode_mark, u32 mask,
event->wd = i_mark->wd;
event->sync_cookie = cookie;
event->name_len = len;
- if (len)
+
+ if (path_bufp) {
+ strcpy(event->name, path_bufp);
+ kfree(path_buf);
+ } else if (len) {
strcpy(event->name, name->name);
+ }

ret = fsnotify_add_event(group, fsn_event, inotify_merge);
if (ret) {
@@ -126,6 +152,13 @@ int inotify_handle_inode_event(struct fsnotify_mark *inode_mark, u32 mask,
fsnotify_destroy_mark(inode_mark, group);

return 0;
+oom:
+ /*
+ * Treat lost event due to ENOMEM the same way as queue
+ * overflow to let userspace know event was lost.
+ */
+ fsnotify_queue_overflow(group);
+ return -ENOMEM;
}

static void inotify_freeing_mark(struct fsnotify_mark *fsn_mark, struct fsnotify_group *group)
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index ed42a189faa2..2a0ad59250ce 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -57,6 +57,7 @@ struct kmem_cache *inotify_inode_mark_cachep __read_mostly;

static long it_zero = 0;
static long it_int_max = INT_MAX;
+static struct inotify_inode_mark *inotify_idr_find(struct fsnotify_group *, int);

static struct ctl_table inotify_table[] = {
{
@@ -110,7 +111,7 @@ static inline __u32 inotify_arg_to_mask(struct inode *inode, u32 arg)
mask |= FS_EVENT_ON_CHILD;

/* mask off the flags used to open the fd */
- mask |= (arg & INOTIFY_USER_MASK);
+ mask |= (arg & (INOTIFY_USER_MASK | IN_FULL_PATHS));

return mask;
}
@@ -203,6 +204,8 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
{
struct inotify_event inotify_event;
struct inotify_event_info *event;
+ struct path event_path;
+ struct inotify_inode_mark *i_mark;
size_t event_size = sizeof(struct inotify_event);
size_t name_len;
size_t pad_name_len;
@@ -210,6 +213,18 @@ static ssize_t copy_event_to_user(struct fsnotify_group *group,
pr_debug("%s: group=%p event=%p\n", __func__, group, fsn_event);

event = INOTIFY_E(fsn_event);
+ /* ensure caller has access to view the full path */
+ if (event->mask & IN_FULL_PATHS && event->mask & IN_MOVE_SELF &&
+ kern_path(event->name, 0, &event_path)) {
+ i_mark = inotify_idr_find(group, event->wd);
+ if (likely(i_mark)) {
+ fsnotify_destroy_mark(&i_mark->fsn_mark, group);
+ /* match ref taken by inotify_idr_find */
+ fsnotify_put_mark(&i_mark->fsn_mark);
+ }
+ return -EACCES;
+ }
+
name_len = event->name_len;
/*
* round up name length so it is a multiple of event_size
@@ -860,7 +875,7 @@ static int __init inotify_user_setup(void)
BUILD_BUG_ON(IN_IGNORED != FS_IN_IGNORED);
BUILD_BUG_ON(IN_ISDIR != FS_ISDIR);

- BUILD_BUG_ON(HWEIGHT32(ALL_INOTIFY_BITS) != 22);
+ BUILD_BUG_ON(HWEIGHT32(ALL_INOTIFY_BITS) != 23);

inotify_inode_mark_cachep = KMEM_CACHE(inotify_inode_mark,
SLAB_PANIC|SLAB_ACCOUNT);
diff --git a/include/linux/inotify.h b/include/linux/inotify.h
index 8d20caa1b268..11db0541cff5 100644
--- a/include/linux/inotify.h
+++ b/include/linux/inotify.h
@@ -15,6 +15,6 @@
IN_DELETE_SELF | IN_MOVE_SELF | IN_UNMOUNT | \
IN_Q_OVERFLOW | IN_IGNORED | IN_ONLYDIR | \
IN_DONT_FOLLOW | IN_EXCL_UNLINK | IN_MASK_ADD | \
- IN_MASK_CREATE | IN_ISDIR | IN_ONESHOT)
+ IN_MASK_CREATE | IN_ISDIR | IN_ONESHOT | IN_FULL_PATHS)

#endif /* _LINUX_INOTIFY_H */
diff --git a/include/uapi/linux/inotify.h b/include/uapi/linux/inotify.h
index 884b4846b630..d95e05aa9bd6 100644
--- a/include/uapi/linux/inotify.h
+++ b/include/uapi/linux/inotify.h
@@ -50,6 +50,7 @@ struct inotify_event {
#define IN_MOVE (IN_MOVED_FROM | IN_MOVED_TO) /* moves */

/* special flags */
+#define IN_FULL_PATHS 0x00800000 /* return the absolute path in the name */
#define IN_ONLYDIR 0x01000000 /* only watch the path if it is a directory */
#define IN_DONT_FOLLOW 0x02000000 /* don't follow a sym link */
#define IN_EXCL_UNLINK 0x04000000 /* exclude events on unlinked objects */
--
2.35.1
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