Re: [PATCH 5/5] vfs: don't allow writes to swap files
From: Al Viro <viro@zeniv.linux.org.uk>
Date: 2019-06-26 03:52:38
Also in:
linux-btrfs, linux-efi, linux-f2fs-devel, linux-fsdevel, linux-mm, linux-xfs, lkml, ocfs2-devel
On Tue, Jun 25, 2019 at 07:33:31PM -0700, Darrick J. Wong wrote:
quoted hunk ↗ jump to hunk
--- a/fs/attr.c +++ b/fs/attr.c@@ -236,6 +236,9 @@ int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **de if (IS_IMMUTABLE(inode)) return -EPERM; + if (IS_SWAPFILE(inode)) + return -ETXTBSY; + if ((ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) && IS_APPEND(inode)) return -EPERM;
Er... So why exactly is e.g. chmod(2) forbidden for swapfiles? Or touch(1), for that matter...
quoted hunk ↗ jump to hunk
diff --git a/mm/swapfile.c b/mm/swapfile.c index 596ac98051c5..1ca4ee8c2d60 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c@@ -3165,6 +3165,19 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags) if (error) goto bad_swap; + /* + * Flush any pending IO and dirty mappings before we start using this + * swap file. + */ + if (S_ISREG(inode->i_mode)) { + inode->i_flags |= S_SWAPFILE; + error = inode_drain_writes(inode); + if (error) { + inode->i_flags &= ~S_SWAPFILE; + goto bad_swap; + } + }
Why are swap partitions any less worthy of protection?