From: Amir Goldstein <amir73il@xxxxxxxxxxxx>
Enforce snapshot file permissions.
Write, truncate and unlink of snapshot inodes is not allowed.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxxxxx>
Signed-off-by: Yongqiang Yang <xiaoqiangnk@xxxxxxxxx>
---
fs/ext4/file.c | 7 +++++++
fs/ext4/inode.c | 7 +++++++
fs/ext4/namei.c | 8 ++++++++
3 files changed, 22 insertions(+), 0 deletions(-)
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 60b3b19..f31e58e 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -168,6 +168,13 @@ static int ext4_file_open(struct inode * inode, struct file * filp)
struct path path;
char buf[64], *cp;
+ if (ext4_snapshot_file(inode) &&
+ (filp->f_flags & O_ACCMODE) != O_RDONLY)
+ /*
+ * allow only read-only access to snapshot files
+ */
+ return -EPERM;
+
if (unlikely(!(sbi->s_mount_flags & EXT4_MF_MNTDIR_SAMPLED) &&
!(sb->s_flags & MS_RDONLY))) {
sbi->s_mount_flags |= EXT4_MF_MNTDIR_SAMPLED;
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index f44f7d3..b210b33 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -4727,6 +4727,13 @@ void ext4_truncate(struct inode *inode)
trace_ext4_truncate_enter(inode);
+ /* prevent truncate of files on snapshot list */
+ if (ext4_snapshot_list(inode)) {
+ snapshot_debug(1, "snapshot (%u) cannot be truncated!\n",
+ inode->i_generation);
+ return;
+ }
+
if (!ext4_can_truncate(inode))
return;
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 93196b6..41df36f 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2225,6 +2225,14 @@ static int ext4_unlink(struct inode *dir, struct dentry *dentry)
inode->i_ino, inode->i_nlink);
inode->i_nlink = 1;
}
+ /* prevent unlink of files on snapshot list */
+ if (inode->i_nlink == 1 &&
+ ext4_snapshot_list(inode)) {
+ snapshot_debug(1, "snapshot (%u) cannot be unlinked!\n",
+ inode->i_generation);
+ retval = -EPERM;
+ goto end_unlink;
+ }
retval = ext4_delete_entry(handle, dir, de, bh);
if (retval)
goto end_unlink;
--
1.7.4.1
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