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Tue, 30 Apr 2024 13:12:51 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 2JzfBVPuMGYVLgAAD6G6ig (envelope-from ); Tue, 30 Apr 2024 13:12:51 +0000 Message-ID: <4e4b7b45-8c3f-4d1f-9507-4f0a9d82835a@suse.cz> Date: Tue, 30 Apr 2024 15:12:50 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/slab: make __free(kfree) accept error pointers Content-Language: en-US To: Dan Carpenter Cc: Matthew Wilcox , Christoph Lameter , Peter Zijlstra , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org, Bartosz Golaszewski , "Lameter, Christopher" References: <285fee25-b447-47a1-9e00-3deb8f9af53e@moroto.mountain> <6a10be7d-b556-42a9-852c-b6ed821ec41e@suse.cz> <49e072da-3d2c-4246-8b7e-7f25513afde3@moroto.mountain> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Queue-Id: 1F42FC0030 X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: r5ep5nkz5hbd9wf5saytn66sqhfkonhc X-HE-Tag: 1714482772-764723 X-HE-Meta: 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 aQmCuInC wpbZCwZadxShrBHFuYtrQ3rJiwlXqPPOTX6ronbArWZdXNeXVYBQ+PzSz3I2fV4oRwUqYAR7la2W8uO6emPDUb0gqmw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/30/24 2:50 PM, Dan Carpenter wrote: > On Tue, Apr 30, 2024 at 02:09:10PM +0200, Vlastimil Babka wrote: >> On 4/29/24 5:03 AM, Matthew Wilcox wrote: >> > On Sun, Apr 28, 2024 at 05:26:44PM +0300, Dan Carpenter wrote: >> >> Currently, if an automatically freed allocation is an error pointer that >> >> will lead to a crash. An example of this is in wm831x_gpio_dbg_show(). >> >> >> >> 171 char *label __free(kfree) = gpiochip_dup_line_label(chip, i); >> >> 172 if (IS_ERR(label)) { >> >> 173 dev_err(wm831x->dev, "Failed to duplicate label\n"); >> >> 174 continue; >> >> 175 } >> >> >> >> The auto clean up function should check for error pointers as well, >> >> otherwise we're going to keep hitting issues like this. >> >> >> >> Fixes: 54da6a092431 ("locking: Introduce __cleanup() based infrastructure") >> >> Cc: >> >> Signed-off-by: Dan Carpenter >> >> --- >> >> Obviously, the fixes tag isn't very fair but it will tell the -stable >> >> tools how far to backport this. >> >> >> >> include/linux/slab.h | 4 ++-- >> >> 1 files changed, 2 insertions(+), 2 deletions(-) >> >> >> >> diff --git a/include/linux/slab.h b/include/linux/slab.h >> >> index 4cc37ef22aae..5f5766219375 100644 >> >> --- a/include/linux/slab.h >> >> +++ b/include/linux/slab.h >> >> @@ -279,7 +279,7 @@ void kfree(const void *objp); >> >> void kfree_sensitive(const void *objp); >> >> size_t __ksize(const void *objp); >> >> >> >> -DEFINE_FREE(kfree, void *, if (_T) kfree(_T)) >> >> +DEFINE_FREE(kfree, void *, if (!IS_ERR_OR_NULL(_T)) kfree(_T)) >> > >> > Wait, why do we check 'if (_T)' at all? kfree() already handles NULL >> > pointers just fine. I wouldn't be averse to making it handle error >> > pointers either. >> >> Making kfree() handle IS_ERR() is perhaps a discussion for something else >> than a stable fix. But Christoph has a point that kfree() checks >> ZERO_OR_NULL_PTR. Here we check IS_ERR_OR_NULL. How about we checked only >> IS_ERR here so it makes some sense? >> > > I wondered why Peter Z wrote it like this as well... I think he did > it so the compiler can figure out which calls to kfree() are unnecessary > and remove them. These functions are inline and kfree() is not. I > haven't measured to see if it actually results in a space savings but > the theory is sound. Hmm that makes sense. There seem to be places that initialize the __free(kfree) variable to NULL and only at some point actually allocate, and between those there are possible returns, i.e. ice_init_hw(). OK, patch applied as-is to slab/for-6.9-rc7/fixes, thanks. > regards, > dan carpenter >