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Date: Wed, 26 Jun 2019 04:51:51 +0100 From: Al Viro <viro@...iv.linux.org.uk> To: "Darrick J. Wong" <darrick.wong@...cle.com> Cc: matthew.garrett@...ula.com, yuchao0@...wei.com, tytso@....edu, ard.biesheuvel@...aro.org, josef@...icpanda.com, hch@...radead.org, clm@...com, adilger.kernel@...ger.ca, jack@...e.com, dsterba@...e.com, jaegeuk@...nel.org, jk@...abs.org, reiserfs-devel@...r.kernel.org, linux-efi@...r.kernel.org, devel@...ts.orangefs.org, linux-kernel@...r.kernel.org, linux-f2fs-devel@...ts.sourceforge.net, linux-xfs@...r.kernel.org, linux-mm@...ck.org, linux-nilfs@...r.kernel.org, linux-mtd@...ts.infradead.org, ocfs2-devel@....oracle.com, linux-fsdevel@...r.kernel.org, linux-ext4@...r.kernel.org, linux-btrfs@...r.kernel.org Subject: Re: [PATCH 5/5] vfs: don't allow writes to swap files On Tue, Jun 25, 2019 at 07:33:31PM -0700, Darrick J. Wong wrote: > --- 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... > 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?
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