From: Gabriel Krisman Bertazi <krisman@suse.de>
To: Eric Biggers <ebiggers@kernel.org>
Cc: brauner@kernel.org, kernel@collabora.com, tytso@mit.edu,
jack@suse.cz, linux-kernel@vger.kernel.org,
Eugen Hristev <eugen.hristev@collabora.com>,
linux-f2fs-devel@lists.sourceforge.net, adilger.kernel@dilger.ca,
viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org,
jaegeuk@kernel.org, linux-ext4@vger.kernel.org,
Gabriel Krisman Bertazi <krisman@collabora.com>
Subject: Re: [f2fs-dev] [PATCH v16 3/9] libfs: Introduce case-insensitive string comparison helper
Date: Sun, 12 May 2024 17:27:48 -0400 [thread overview]
Message-ID: <875xviyb3f.fsf@mailhost.krisman.be> (raw)
In-Reply-To: <20240510013330.GI1110919@google.com> (Eric Biggers's message of "Fri, 10 May 2024 01:33:30 +0000")
Eric Biggers <ebiggers@kernel.org> writes:
> On Fri, Apr 05, 2024 at 03:13:26PM +0300, Eugen Hristev wrote:
>> + if (WARN_ON_ONCE(!fscrypt_has_encryption_key(parent)))
>> + return -EINVAL;
>> +
>> + decrypted_name.name = kmalloc(de_name_len, GFP_KERNEL);
>> + if (!decrypted_name.name)
>> + return -ENOMEM;
>> + res = fscrypt_fname_disk_to_usr(parent, 0, 0, &encrypted_name,
>> + &decrypted_name);
>> + if (res < 0)
>> + goto out;
>
> If fscrypt_fname_disk_to_usr() returns an error and !sb_has_strict_encoding(sb),
> then this function returns 0 (indicating no match) instead of the error code
> (indicating an error). Is that the correct behavior? I would think that
> strict_encoding should only have an effect on the actual name
> comparison.
No. we *want* this return code to be propagated back to f2fs. In ext4 it
wouldn't matter since the error is not visible outside of ext4_match,
but f2fs does the right thing and stops the lookup.
Thinking about it, there is a second problem with this series.
Currently, if we are on strict_mode, f2fs_match_ci_name does not
propagate unicode errors back to f2fs. So, once a utf8 invalid sequence
is found during lookup, it will be considered not-a-match but the lookup
will continue. This allows some lookups to succeed even in a corrupted
directory. With this patch, we will abort the lookup on the first
error, breaking existing semantics. Note that these are different from
memory allocation failure and fscrypt_fname_disk_to_usr. For those, it
makes sense to abort.
Also, once patch 6 and 7 are added, if fscrypt fails with -EINVAL for
any reason unrelated to unicode (like in the WARN_ON above), we will
incorrectly print the error message saying there is a bad UTF8 string.
My suggestion would be to keep the current behavior. Make
generic_ci_match only propagate non-unicode related errors back to the
filesystem. This means that we need to move the error messages in patch
6 and 7 into this function, so they only trigger when utf8_strncasecmp*
itself fails.
>> + /*
>> + * Attempt a case-sensitive match first. It is cheaper and
>> + * should cover most lookups, including all the sane
>> + * applications that expect a case-sensitive filesystem.
>> + */
>> + if (folded_name->name) {
>> + if (dirent.len == folded_name->len &&
>> + !memcmp(folded_name->name, dirent.name, dirent.len))
>> + goto out;
>> + res = utf8_strncasecmp_folded(um, folded_name, &dirent);
>
> Shouldn't the memcmp be done with the original user-specified name, not the
> casefolded name? I would think that the user-specified name is the one that's
> more likely to match the on-disk name, because of case preservation. In most
> cases users will specify the same case on both file creation and later access.
Yes.
--
Gabriel Krisman Bertazi
_______________________________________________
Linux-f2fs-devel mailing list
Linux-f2fs-devel@lists.sourceforge.net
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next prev parent reply other threads:[~2024-05-12 21:28 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-05 12:13 [f2fs-dev] [PATCH v16 0/9] Cache insensitive cleanup for ext4/f2fs Eugen Hristev via Linux-f2fs-devel
2024-04-05 12:13 ` [f2fs-dev] [PATCH v16 1/9] ext4: Simplify the handling of cached insensitive names Eugen Hristev via Linux-f2fs-devel
2024-05-10 1:23 ` Eric Biggers
2024-04-05 12:13 ` [f2fs-dev] [PATCH v16 2/9] f2fs: " Eugen Hristev via Linux-f2fs-devel
2024-05-10 1:23 ` Eric Biggers
2024-04-05 12:13 ` [f2fs-dev] [PATCH v16 3/9] libfs: Introduce case-insensitive string comparison helper Eugen Hristev via Linux-f2fs-devel
2024-05-10 1:33 ` Eric Biggers
2024-05-12 21:27 ` Gabriel Krisman Bertazi [this message]
2024-05-22 14:02 ` Eugen Hristev via Linux-f2fs-devel
2024-05-22 23:05 ` Gabriel Krisman Bertazi
2024-05-26 11:49 ` Eugen Hristev via Linux-f2fs-devel
2024-05-27 20:54 ` Gabriel Krisman Bertazi
2024-04-05 12:13 ` [f2fs-dev] [PATCH v16 4/9] ext4: Reuse generic_ci_match for ci comparisons Eugen Hristev via Linux-f2fs-devel
2024-05-10 1:23 ` Eric Biggers
2024-04-05 12:13 ` [f2fs-dev] [PATCH v16 5/9] f2fs: " Eugen Hristev via Linux-f2fs-devel
2024-05-10 1:24 ` Eric Biggers
2024-04-05 12:13 ` [f2fs-dev] [PATCH v16 6/9] ext4: Log error when lookup of encoded dentry fails Eugen Hristev via Linux-f2fs-devel
2024-05-10 1:24 ` Eric Biggers
2024-04-05 12:13 ` [f2fs-dev] [PATCH v16 7/9] f2fs: " Eugen Hristev via Linux-f2fs-devel
2024-05-10 1:25 ` Eric Biggers
2024-04-05 12:13 ` [f2fs-dev] [PATCH v16 8/9] ext4: Move CONFIG_UNICODE defguards into the code flow Eugen Hristev via Linux-f2fs-devel
2024-05-10 1:25 ` Eric Biggers
2024-04-05 12:13 ` [f2fs-dev] [PATCH v16 9/9] f2fs: " Eugen Hristev via Linux-f2fs-devel
2024-05-10 1:25 ` Eric Biggers
2024-04-05 12:18 ` [f2fs-dev] [PATCH v16 0/9] Cache insensitive cleanup for ext4/f2fs Matthew Wilcox
2024-04-05 13:02 ` Eugen Hristev via Linux-f2fs-devel
2024-04-05 16:37 ` Gabriel Krisman Bertazi
2024-05-09 15:12 ` Eugen Hristev via Linux-f2fs-devel
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