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Tue, 1 Oct 2024 15:39:13 +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 u66vNaEX/GYiOAAAD6G6ig (envelope-from ); Tue, 01 Oct 2024 15:39:13 +0000 Message-ID: <73e499a7-6237-4f67-84c1-d6434b89df26@suse.cz> Date: Tue, 1 Oct 2024 17:39:13 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm, slab: fix use of SLAB_SUPPORTS_SYSFS in kmem_cache_release() To: Hyeonggon Yoo <42.hyeyoo@gmail.com>, Nilay Shroff Cc: linux-mm@kvack.org, linux-block@vger.kernel.org, akpm@linux-foundation.org, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, roman.gushchin@linux.dev, yi.zhang@redhat.com, shinichiro.kawasaki@wdc.com, axboe@kernel.dk, gjoyce@linux.ibm.com References: <20241001140245.306087-1-nilay@linux.ibm.com> Content-Language: en-US From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Queue-Id: ABDCC160024 X-Stat-Signature: mfzw4zuc811n9ner867whw6buwmzskiz X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1727797155-228262 X-HE-Meta: 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 0EOM7pbD 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 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 10/1/24 16:50, Hyeonggon Yoo wrote: > On Tue, Oct 1, 2024 at 11:02 PM Nilay Shroff wrote: >> >> The fix implemented in commit 4ec10268ed98 ("mm, slab: unlink slabinfo, >> sysfs and debugfs immediately") caused a subtle side effect due to which >> while destroying the kmem cache, the code path would never get into >> sysfs_slab_release() function even though SLAB_SUPPORTS_SYSFS is defined >> and slab state is FULL. Due to this side effect, we would never release >> kobject defined for kmem cache and leak the associated memory. >> >> The issue here's with the use of __is_defined() macro in kmem_cache_ >> release(). The __is_defined() macro expands to __take_second_arg( >> arg1_or_junk 1, 0). If "arg1_or_junk" is defined to 1 then it expands to >> __take_second_arg(0, 1, 0) and returns 1. If "arg1_or_junk" is NOT defined >> to any value then it expands to __take_second_arg(... 1, 0) and returns 0. >> >> In this particular issue, SLAB_SUPPORTS_SYSFS is defined without any >> associated value and that causes __is_defined(SLAB_SUPPORTS_SYSFS) to >> always evaluate to 0 and hence it would never invoke sysfs_slab_release(). >> >> This patch helps fix this issue by defining SLAB_SUPPORTS_SYSFS to 1. Oops, thanks a lot for debugging and fixing this! > > Hi Nilay, > > Thanks for your effort in investigating the issue and fixing it! > This makes sense to me, but is there any reason the code avoids using > IS_ENABLED()? > > I think technically either IS_ENABLED() or __is_defined() (with your > fix) would work > in this case, but it made me think "What is the difference between > IS_ENABLED() and __is_defined()?" > > IS_ENABLED() is already frequently used in mm and only few code snippets use > __is_defined() directly. I was wary of using IS_ENABLED() because that's intended for CONFIG_ macros and SLAB_SUPPORTS_SYSFS isn't one, so even if it worked now, it wouldn't be guaranteed to stay working. > Best, > Hyeonggon > >> Fixes: 4ec10268ed98 ("mm, slab: unlink slabinfo, sysfs and debugfs immediately") >> Reported-by: Yi Zhang >> Closes: https://lore.kernel.org/all/CAHj4cs9YCCcfmdxN43-9H3HnTYQsRtTYw1Kzq-L468GfLKAENA@mail.gmail.com/ >> Signed-off-by: Nilay Shroff >> --- >> mm/slab.h | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/mm/slab.h b/mm/slab.h >> index f22fb760b286..3e0a08ea4c42 100644 >> --- a/mm/slab.h >> +++ b/mm/slab.h >> @@ -310,7 +310,7 @@ struct kmem_cache { >> }; >> >> #if defined(CONFIG_SYSFS) && !defined(CONFIG_SLUB_TINY) >> -#define SLAB_SUPPORTS_SYSFS >> +#define SLAB_SUPPORTS_SYSFS 1 >> void sysfs_slab_unlink(struct kmem_cache *s); >> void sysfs_slab_release(struct kmem_cache *s); >> #else >> -- >> 2.45.2 >>