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[91.159.24.186]) by smtp.gmail.com with ESMTPSA id 2adb3069b0e04-5aa2f15783csm166677e87.83.2026.05.21.04.24.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 21 May 2026 04:24:22 -0700 (PDT) Message-ID: Date: Thu, 21 May 2026 14:24:12 +0300 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/slab: fix probable issue of dentries registration under /sys/kernel/slab To: Harry Yoo , Vlastimil Babka , Andrew Morton , Christoph Lameter , Hao Li Cc: David Rientjes , Roman Gushchin , Hugh Dickins , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260520011019.1707010-1-vladimir.zapolskiy@linaro.org> <8a80496b-1568-4a0b-a878-836c27d19ad5@kernel.org> From: Vladimir Zapolskiy In-Reply-To: <8a80496b-1568-4a0b-a878-836c27d19ad5@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Harry, On 5/20/26 06:42, Harry Yoo wrote: > > > On 5/20/26 10:10 AM, Vladimir Zapolskiy wrote: >> L2TP/IP and L2TP/IPv6 protocol names contain a slash symbol, however these >> names are blindly used as symlinks to slab cache objects registered under >> /sys/kernel/slab. This kind of symlink creation is successful, but its >> dentry is obviously broken, as well it breaks the access to the list of >> /sys/kernel/slab dentries. > > Oops. I just loaded l2tp_ip module and it indeed broke it. > > $ ls > ls: reading directory '.': Input/output error > :0000136/ kmalloc-rnd-01-16/ kmalloc-rnd-15-32/ > :0000192/ kmalloc-rnd-02-512/ memdup_user-32/ > :0000560/ kmalloc-rnd-06-192/ memdup_user-4k/ > :0000768/ kmalloc-rnd-06-512/ pde_opener@ > :a-0000168/ kmalloc-rnd-07-4k/ pidfs_xattr_cache@ > :A-0000184/ kmalloc-rnd-11-8/ RAWv6/ > audit_buffer@ kmalloc-rnd-11-96/ rpc_inode_cache/ > configfs_dir_cache@ kmalloc-rnd-12-4k/ task_delay_info@ > ecryptfs_global_auth_tok_cache@ kmalloc-rnd-13-128/ TCPv6/ > fscache_cookie_jar@ kmalloc-rnd-14-96/ > io_kiocb/ kmalloc-rnd-15-2k/ > >> Likely L2TP protocol renames cannot be done, since the defined protocol >> names are exposed over /proc/net/protocols for years, but the symlink >> names can be renamed, because they are yet to be properly created, and >> this should be eventually done by this change. >> >> The problem manifests itself, if CONFIG_L2TP_IP build symbol is selected. >> >> Fixes: 81819f0fc8285 ("SLUB core") >> Signed-off-by: Vladimir Zapolskiy >> --- > > There is also a debugfs feature that would cause a similar issue. thank you for review, I've just sent v2 fixing __kmem_cache_create_args() side. As for debugfs I haven't reproduced any similar issue, please give me a clue here, also likely any non-slab changes should be done separately. > Can we replace '/' in the cache name, without renaming the protocol name? > I believe that's exactly how it's done, the protocol name is left unchanged. -- Best wishes, Vladimir