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authorEric Biggers <ebiggers@google.com>2019-07-22 18:26:22 +0200
committerEric Biggers <ebiggers@google.com>2019-07-29 01:59:16 +0200
commitc1d9b584e2cf3f0562d8fcf34574c044d17853a1 (patch)
tree9c0c25b8bb3e53a55ffb9d86faae9cff7c56d012 /fs/verity
parentfs-verity: add the hook for file ->open() (diff)
downloadlinux-c1d9b584e2cf3f0562d8fcf34574c044d17853a1.tar.xz
linux-c1d9b584e2cf3f0562d8fcf34574c044d17853a1.zip
fs-verity: add the hook for file ->setattr()
Add a function fsverity_prepare_setattr() which filesystems that support fs-verity must call to deny truncates of verity files. Reviewed-by: Theodore Ts'o <tytso@mit.edu> Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org> Signed-off-by: Eric Biggers <ebiggers@google.com>
Diffstat (limited to 'fs/verity')
-rw-r--r--fs/verity/open.c21
1 files changed, 21 insertions, 0 deletions
diff --git a/fs/verity/open.c b/fs/verity/open.c
index 8013f77f907e..2cb2fe8082bf 100644
--- a/fs/verity/open.c
+++ b/fs/verity/open.c
@@ -296,6 +296,27 @@ int fsverity_file_open(struct inode *inode, struct file *filp)
EXPORT_SYMBOL_GPL(fsverity_file_open);
/**
+ * fsverity_prepare_setattr() - prepare to change a verity inode's attributes
+ * @dentry: dentry through which the inode is being changed
+ * @attr: attributes to change
+ *
+ * Verity files are immutable, so deny truncates. This isn't covered by the
+ * open-time check because sys_truncate() takes a path, not a file descriptor.
+ *
+ * Return: 0 on success, -errno on failure
+ */
+int fsverity_prepare_setattr(struct dentry *dentry, struct iattr *attr)
+{
+ if (IS_VERITY(d_inode(dentry)) && (attr->ia_valid & ATTR_SIZE)) {
+ pr_debug("Denying truncate of verity file (ino %lu)\n",
+ d_inode(dentry)->i_ino);
+ return -EPERM;
+ }
+ return 0;
+}
+EXPORT_SYMBOL_GPL(fsverity_prepare_setattr);
+
+/**
* fsverity_cleanup_inode() - free the inode's verity info, if present
*
* Filesystems must call this on inode eviction to free ->i_verity_info.