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[46.53.134.148]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4505285e765sm19800064f8f.10.2026.05.07.06.48.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 07 May 2026 06:48:48 -0700 (PDT) Date: Thu, 7 May 2026 16:51:10 +0300 From: Alexey Dobriyan To: Greg Kroah-Hartman Cc: "Rafael J. Wysocki" , Danilo Krummrich , linux-fsdevel@vger.kernel.org Subject: Re: [PATCH] sysfs: upgrade OOB write by buggy .show hook into WARNing Message-ID: References: <5f794f46-5afd-405c-9747-76f2c95d4598@p183> <3cc3e8c6-c6e8-4625-a88f-f5708b935dab@p183> <2026050720-plating-cling-153a@gregkh> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <2026050720-plating-cling-153a@gregkh> On Thu, May 07, 2026 at 11:05:16AM +0200, Greg Kroah-Hartman wrote: > On Thu, May 07, 2026 at 12:01:43PM +0300, Alexey Dobriyan wrote: > > --- a/fs/sysfs/file.c > > +++ b/fs/sysfs/file.c > > @@ -70,9 +70,8 @@ static int sysfs_kf_seq_show(struct seq_file *sf, void *v) > > * The code works fine with PAGE_SIZE return but it's likely to > > * indicate truncated result or overflow in normal use cases. > > */ > > - if (count >= (ssize_t)PAGE_SIZE) { > > - printk("fill_read_buffer: %pS returned bad count\n", > > - ops->show); > > + if (count >= PAGE_SIZE) { > > + WARN(1, "OOB write or bad count %zd at %pS\n", count, ops->show); > > This is going to be interesting to see what triggers, so I'll go queue > this up soon. > > And this implies you did hit this on ext4? The check was triggered by out-of-tree module. ext4 is me testing the patch with a custom written buggy hook. /sys/alexey