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Wed, 22 May 2024 14:02:54 +0000 (UTC) Message-ID: <9afebadd-765f-42f3-a80b-366dd749bf48@collabora.com> Date: Wed, 22 May 2024 17:02:53 +0300 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird To: Gabriel Krisman Bertazi , Eric Biggers References: <20240405121332.689228-1-eugen.hristev@collabora.com> <20240405121332.689228-4-eugen.hristev@collabora.com> <20240510013330.GI1110919@google.com> <875xviyb3f.fsf@mailhost.krisman.be> Content-Language: en-US In-Reply-To: <875xviyb3f.fsf@mailhost.krisman.be> X-Headers-End: 1s9mYd-0001wx-GB Subject: Re: [f2fs-dev] [PATCH v16 3/9] libfs: Introduce case-insensitive string comparison helper X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Eugen Hristev via Linux-f2fs-devel Reply-To: Eugen Hristev Cc: brauner@kernel.org, kernel@collabora.com, tytso@mit.edu, jack@suse.cz, linux-kernel@vger.kernel.org, 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 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On 5/13/24 00:27, Gabriel Krisman Bertazi wrote: > Eric Biggers 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. In the previous version which I sent, you told me that the error should be propagated only in strict_mode, and if !strict_mode, it should just return no match. Originally I did not understand that this should be done only for utf8_strncasecmp errors, and not for all the errors. I will change it here to fix that. > > 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. So , in the case of f2fs , we must not propagate utf8 errors ? It should just return no match even in strict mode ? If this helper is common for both f2fs and ext4, we have to do the same for ext4 ? Or we are no longer able to commonize the code altogether ? > > 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. > So basically unicode errors stop here, and print the error message here in that case. Am I understanding it correctly ? >>> + /* >>> + * 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. > so the utf8_strncasecmp_folded call here must use name->name instead of folded_name ? Thanks for the review Eugen _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel