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authorMark Fasheh <mfasheh@suse.de>2018-09-10 16:21:17 -0700
committerAl Viro <viro@zeniv.linux.org.uk>2018-10-17 21:15:39 -0400
commit5de4480ae7f8f1969065aa88be98111e36075bb0 (patch)
treee0dfb1a023f4e49e16176d072b31e51f8d1f8f80 /fs/read_write.c
parent995f608e7a349c837d6c0b3ffa7d1a94d01f7203 (diff)
vfs: allow dedupe of user owned read-only files
The permission check in vfs_dedupe_file_range_one() is too coarse - We only allow dedupe of the destination file if the user is root, or they have the file open for write. This effectively limits a non-root user from deduping their own read-only files. In addition, the write file descriptor that the user is forced to hold open can prevent execution of files. As file data during a dedupe does not change, the behavior is unexpected and this has caused a number of issue reports. For an example, see: https://github.com/markfasheh/duperemove/issues/129 So change the check so we allow dedupe on the target if: - the root or admin is asking for it - the process has write access - the owner of the file is asking for the dedupe - the process could get write access That way users can open read-only and still get dedupe. Signed-off-by: Mark Fasheh <mfasheh@suse.de> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/read_write.c')
-rw-r--r--fs/read_write.c16
1 files changed, 15 insertions, 1 deletions
diff --git a/fs/read_write.c b/fs/read_write.c
index 39b4a21dd933..be0e8723a049 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -1964,6 +1964,20 @@ out_error:
}
EXPORT_SYMBOL(vfs_dedupe_file_range_compare);
+/* Check whether we are allowed to dedupe the destination file */
+static bool allow_file_dedupe(struct file *file)
+{
+ if (capable(CAP_SYS_ADMIN))
+ return true;
+ if (file->f_mode & FMODE_WRITE)
+ return true;
+ if (uid_eq(current_fsuid(), file_inode(file)->i_uid))
+ return true;
+ if (!inode_permission(file_inode(file), MAY_WRITE))
+ return true;
+ return false;
+}
+
int vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
struct file *dst_file, loff_t dst_pos, u64 len)
{
@@ -1978,7 +1992,7 @@ int vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos,
goto out_drop_write;
ret = -EINVAL;
- if (!(capable(CAP_SYS_ADMIN) || (dst_file->f_mode & FMODE_WRITE)))
+ if (!allow_file_dedupe(dst_file))
goto out_drop_write;
ret = -EXDEV;