From: Al Viro <viro@zeniv.linux.org.uk>
To: Gabriel Krisman Bertazi <krisman@suse.de>
Cc: brauner@kernel.org, tytso@mit.edu, ebiggers@kernel.org,
jaegeuk@kernel.org, linux-fsdevel@vger.kernel.org,
linux-ext4@vger.kernel.org,
linux-f2fs-devel@lists.sourceforge.net,
Gabriel Krisman Bertazi <krisman@collabora.com>
Subject: Re: [PATCH v6 5/9] libfs: Validate negative dentries in case-insensitive directories
Date: Wed, 22 Nov 2023 20:20:44 +0000 [thread overview]
Message-ID: <20231122202044.GF38156@ZenIV> (raw)
In-Reply-To: <20230816050803.15660-6-krisman@suse.de>
On Wed, Aug 16, 2023 at 01:07:59AM -0400, Gabriel Krisman Bertazi wrote:
> +static int generic_ci_d_revalidate(struct dentry *dentry,
> + const struct qstr *name,
> + unsigned int flags)
> +{
> + const struct dentry *parent;
> + const struct inode *dir;
> +
> + if (!d_is_negative(dentry))
> + return 1;
> +
> + parent = READ_ONCE(dentry->d_parent);
> + dir = READ_ONCE(parent->d_inode);
> +
> + if (!dir || !IS_CASEFOLDED(dir))
> + return 1;
> +
> + /*
> + * Negative dentries created prior to turning the directory
> + * case-insensitive cannot be trusted, since they don't ensure
> + * any possible case version of the filename doesn't exist.
> + */
> + if (!d_is_casefolded_name(dentry))
> + return 0;
> +
> + /*
> + * If the lookup is for creation, then a negative dentry can only be
> + * reused if it's a case-sensitive match, not just a case-insensitive
> + * one. This is needed to make the new file be created with the name
> + * the user specified, preserving case.
> + *
> + * LOOKUP_CREATE or LOOKUP_RENAME_TARGET cover most creations. In these
> + * cases, ->d_name is stable and can be compared to 'name' without
> + * taking ->d_lock because the caller must hold dir->i_rwsem. (This
> + * is because the directory lock blocks the dentry from being
> + * concurrently instantiated, and negative dentries are never moved.)
> + *
> + * All other creations actually use flags==0. These come from the edge
> + * case of filesystems calling functions like lookup_one() that do a
> + * lookup without setting the lookup flags at all. Such lookups might
> + * or might not be for creation, and if not don't guarantee stable
> + * ->d_name. Therefore, invalidate all negative dentries when flags==0.
> + */
> + if (flags & (LOOKUP_CREATE | LOOKUP_RENAME_TARGET)) {
> + if (dentry->d_name.len != name->len ||
> + memcmp(dentry->d_name.name, name->name, name->len))
> + return 0;
Frankly, I would rather moved that to fs/dcache.c and used dentry_cmp() instead
of memcmp() here. Avoids the discussion of ->d_name stability for this one.
next prev parent reply other threads:[~2023-11-22 20:20 UTC|newest]
Thread overview: 65+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-16 5:07 [PATCH v6 0/9] Support negative dentries on case-insensitive ext4 and f2fs Gabriel Krisman Bertazi
2023-08-16 5:07 ` [PATCH v6 1/9] ecryptfs: Reject casefold directory inodes Gabriel Krisman Bertazi
2023-08-16 5:07 ` [PATCH v6 2/9] 9p: Split ->weak_revalidate from ->revalidate Gabriel Krisman Bertazi
2023-08-16 5:07 ` [PATCH v6 3/9] fs: Expose name under lookup to d_revalidate hooks Gabriel Krisman Bertazi
2023-11-22 20:59 ` Al Viro
2023-08-16 5:07 ` [PATCH v6 4/9] fs: Add DCACHE_CASEFOLDED_NAME flag Gabriel Krisman Bertazi
2023-11-22 20:32 ` Al Viro
2023-08-16 5:07 ` [PATCH v6 5/9] libfs: Validate negative dentries in case-insensitive directories Gabriel Krisman Bertazi
2023-11-22 20:20 ` Al Viro [this message]
2023-08-16 5:08 ` [PATCH v6 6/9] libfs: Chain encryption checks after case-insensitive revalidation Gabriel Krisman Bertazi
2023-08-16 5:08 ` [PATCH v6 7/9] libfs: Merge encrypted_ci_dentry_ops and ci_dentry_ops Gabriel Krisman Bertazi
2023-08-16 5:08 ` [PATCH v6 8/9] ext4: Enable negative dentries on case-insensitive lookup Gabriel Krisman Bertazi
2023-08-16 5:08 ` [PATCH v6 9/9] f2fs: " Gabriel Krisman Bertazi
2023-08-17 17:06 ` [PATCH v6 0/9] Support negative dentries on case-insensitive ext4 and f2fs Eric Biggers
2023-08-21 15:52 ` Christian Brauner
2023-08-21 18:53 ` Gabriel Krisman Bertazi
2023-08-22 9:03 ` Christian Brauner
2023-10-24 22:20 ` Gabriel Krisman Bertazi
2023-10-25 13:32 ` Christian Brauner
2023-10-25 15:19 ` Gabriel Krisman Bertazi
2023-11-19 23:11 ` [f2fs-dev] " Gabriel Krisman Bertazi
[not found] ` <655a9634.630a0220.d50d7.5063SMTPIN_ADDED_BROKEN@mx.google.com>
2023-11-20 15:06 ` Christian Brauner
2023-11-20 16:59 ` Gabriel Krisman Bertazi
2023-11-20 18:07 ` Linus Torvalds
2023-11-21 2:02 ` Theodore Ts'o
2023-11-21 2:29 ` Linus Torvalds
2023-11-21 3:03 ` Linus Torvalds
2023-11-21 5:12 ` Theodore Ts'o
2023-11-22 21:04 ` Al Viro
2023-11-21 2:27 ` Al Viro
2023-11-22 21:19 ` Al Viro
2023-11-23 0:18 ` Linus Torvalds
2023-11-23 5:09 ` Al Viro
2023-11-23 15:57 ` Gabriel Krisman Bertazi
2023-11-23 17:12 ` Al Viro
2023-11-23 17:37 ` Gabriel Krisman Bertazi
2023-11-23 18:24 ` Al Viro
2023-11-23 19:06 ` Gabriel Krisman Bertazi
2023-11-23 19:53 ` Al Viro
2023-11-23 20:15 ` Al Viro
2023-11-24 15:20 ` Gabriel Krisman Bertazi
2023-11-28 0:02 ` Al Viro
2023-11-23 21:52 ` Al Viro
2023-11-24 15:22 ` Gabriel Krisman Bertazi
2023-11-25 22:01 ` Al Viro
2023-11-26 4:52 ` Al Viro
2023-11-26 18:41 ` fun with d_invalidate() vs. d_splice_alias() was " Al Viro
2023-11-27 6:38 ` Al Viro
2023-11-27 15:47 ` Eric W. Biederman
2023-11-27 16:01 ` Eric W. Biederman
2023-11-27 17:25 ` Al Viro
2023-11-27 18:26 ` Al Viro
2023-11-27 16:03 ` Al Viro
2023-11-27 16:14 ` Al Viro
2023-11-27 18:19 ` Eric W. Biederman
2023-11-27 18:43 ` Al Viro
2023-11-27 16:33 ` Christian Brauner
2023-11-29 4:53 ` Al Viro
2023-11-29 10:21 ` Christian Brauner
2023-11-29 15:19 ` Eric W. Biederman
[not found] ` <655f7665.df0a0220.58a21.e84fSMTPIN_ADDED_BROKEN@mx.google.com>
2023-11-23 16:41 ` Linus Torvalds
2023-11-23 1:12 ` Al Viro
2023-11-23 1:22 ` Al Viro
2023-11-22 3:30 ` Gabriel Krisman Bertazi
2024-01-16 19:02 ` patchwork-bot+f2fs
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