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Wed, 07 May 2025 11:20:32 -0700 (PDT) Message-ID: Date: Wed, 7 May 2025 20:20:31 +0200 Precedence: bulk X-Mailing-List: linux-modules@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] module: ensure that kobject_put() is safe for module type kobjects To: Dmitry Antipov Cc: Luis Chamberlain , Sami Tolvanen , Daniel Gomez , Shyam Saini , linux-modules@vger.kernel.org, syzbot+7fb8a372e1f6add936dd@syzkaller.appspotmail.com References: <443b9765-3677-4bff-a6b6-a89f6c73cb67@suse.com> <20250507065044.86529-1-dmantipov@yandex.ru> Content-Language: en-US From: Petr Pavlu In-Reply-To: <20250507065044.86529-1-dmantipov@yandex.ru> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 5/7/25 08:50, Dmitry Antipov wrote: > In 'lookup_or_create_module_kobject()', an internal kobject is created > using 'module_ktype'. So call to 'kobject_put()' on error handling > path causes an attempt to use an uninitialized completion pointer in > 'module_kobject_release()'. In this scenario, we just want to release > kobject without an extra synchronization required for a regular module > unloading process, so adding an extra check whether 'complete()' is > actually required makes 'kobject_put()' safe. > > Reported-by: syzbot+7fb8a372e1f6add936dd@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=7fb8a372e1f6add936dd > Fixes: 942e443127e9 ("module: Fix mod->mkobj.kobj potentially freed too early") > Suggested-by: Petr Pavlu > Signed-off-by: Dmitry Antipov Added on modules-fixes. I plan to send the fix to Linus on Friday. While the underlying problem was already there, commit f95bbfe18512 ("drivers: base: handle module_kobject creation"), merged in v6.15-rc5, made it more exposed and I think it's better to have it fixed in this cycle. The patch itself is also safe. -- Thanks, Petr