Commit 1ca551c6 authored Mar 05, 2011 by Marco Stornelli Committed by Al Viro Mar 10, 2011

Check for immutable/append flag in fallocate path

In the fallocate path the kernel doesn't check for the immutable/append
flag. It's possible to have a race condition in this scenario: an
application open a file in read/write and it does something, meanwhile
root set the immutable flag on the file, the application at that point
can call fallocate with success. In addition, we don't allow to do any
unreserve operation on an append only file but only the reserve one.

Signed-off-by: Marco Stornelli <marco.stornelli@gmail.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

parent 991ac30d

fs/open.c

+8 −0

Original line number	Diff line number	Diff line
		@@ -233,6 +233,14 @@ int do_fallocate(struct file *file, int mode, loff_t offset, loff_t len)

		if (!(file->f_mode & FMODE_WRITE))
		return -EBADF;

		/* It's not possible punch hole on append only file */
		if (mode & FALLOC_FL_PUNCH_HOLE && IS_APPEND(inode))
		return -EPERM;

		if (IS_IMMUTABLE(inode))
		return -EPERM;

		/*
		* Revalidate the write permissions, in case security policy has
		* changed since the files were opened.

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