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Wed, 28 Aug 2024 16:53:11 +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 G265KPdVz2bNawAAD6G6ig (envelope-from ); Wed, 28 Aug 2024 16:53:11 +0000 Message-ID: <7c0d1d9f-f233-47a4-87fe-d01c348d7787@suse.cz> Date: Wed, 28 Aug 2024 18:53:11 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V1] mm, slub: avoid zeroing kmalloc redzone Content-Language: en-US To: Feng Tang , "Peng Fan (OSS)" Cc: nicolas.bouchinet@clip-os.org, chengming.zhou@linux.dev, Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Andrew Morton , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, "open list:SLAB ALLOCATOR" , open list , Peng Fan References: <20240823062415.3632189-1-peng.fan@oss.nxp.com> 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: 7bit X-Stat-Signature: 14q13kxyz6mkmj3k44iytmfjywjmbdco X-Rspamd-Queue-Id: E54D940007 X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1724863994-616428 X-HE-Meta: U2FsdGVkX1/L9ASbcgRvko++TP8sk9srpE8LHL1udJxtbTzXy8ViXg5RG7vodCJTn2mwsIXBFVWdaBjqShn4of+DBqbe7PKTATcSPKD+gDMgO94QxsDIhV2jrLY2rl69gXniqDcp8P9bCZEhg1x0TiuEAn8bl95Bc1MC6WvBprbi2ofY6y66Uj8DVfKBfsWGoTdKMyTLhPuQfINVfgAdkBjVqY/kXkcDgsyDPwPhVdW3NwRE3/OnPfCOMbvgnPomgUVASLxioy4Z8sBwjWipLNEXUPbyARF5uE/up+mLU8/Nz2FaIgQWd6L0EQfnBOsHo6pQkWG5beDFXSu9uIz//hXK9rJgAdISeJFlsD2PSXi3cXE0XKQDDh2B+uoCBK9AeZjCvLSU3mWK/gxrL253KiuKWVafJLvXf5jM1JQ2mRZBLgdn1rV6bcdt9S/3e5ecY9whH45juDpNmiVa28lzEHr4kzqdNHlvK20TMF5oYMt48sQtAEq+dCBAKIEmAQhPivhFYScWP6VLiM1J5WnskDNEMabNGYgdPif4lLVN7ywdm2JpAGjpiyt1PardH+Gk3L+N2N61zt+Z7h0DhfP4HNgVs2E/oe4MCph6uWRGH5VME8q42aik1ig468QJZgM80zVe6PYoXNFLcWiKO8FayEk61HcVEwMT30QnXcqjW6Dp+vOGlr7lDhGA9o0dWjM+Qjao6yzEZgVsnAG/ZFoao7XTXSIRV9MCoRKVZ5GgcgedIXsIsVTASioCO1hqyLxHmYseHDQgTyQ/vNEjoFln607FnLrEViGfNhTmM7uxm2Uno8XbBz/qqKelqN1ObfR6OcxFBjNOHfiHYLkAvPtgyEamCsFNZXgejI89uhM2Ft3lYxguN8lJRPYMUJ6nefOl6KZ+n+ikoSblME6u74zIRptk2+Mis0pncRNeZlUkdvv3Sr1SLdSK8++of7EiomSD6FeK86X+CKwZ+rbS0Wk FF1KfapF 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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 8/25/24 15:05, Feng Tang wrote: > On Fri, Aug 23, 2024 at 02:24:15PM +0800, Peng Fan (OSS) wrote: >> From: Peng Fan >> >> With commit 946fa0dbf2d8 >> ("mm/slub: extend redzone check to extra allocated kmalloc space than requested"), >> setting orig_size treats the wasted space (object_size - orig_size) as >> redzones. But (in check_object()) when orig_size is set to zero, the entire >> object is perceived as a redzone. To a valid allocated kmalloc space, >> when init_on_free=1, the wasted space and the orig_size should >> not be cleared to 0, otherwise there will be kernel dump: Could we make it more clear? Since commit 946fa0dbf2d8 ("mm/slub: extend redzone check to extra allocated kmalloc space than requested"), setting orig_size treats the wasted space (object_size - orig_size) as a redzone. However with init_on_free=1 we clear the full object->size, including the redzone. Additionally we clear the object metadata, including the stored orig_size, making it zero, which makes check_object() treat the the whole object as a redzone. These issues lead to the following BUG report with "slub_debug=FUZ init_on_free=1": >> >> [ 0.000000] ============================================================================= >> [ 0.000000] BUG kmalloc-8 (Not tainted): kmalloc Redzone overwritten >> [ 0.000000] ----------------------------------------------------------------------------- >> [ 0.000000] >> [ 0.000000] 0xffff000010032858-0xffff00001003285f @offset=2136. First byte 0x0 instead of 0xcc >> [ 0.000000] FIX kmalloc-8: Restoring kmalloc Redzone 0xffff000010032858-0xffff00001003285f=0xcc >> [ 0.000000] Slab 0xfffffdffc0400c80 objects=36 used=23 fp=0xffff000010032a18 flags=0x3fffe0000000200(workingset|node=0|zone=0|lastcpupid=0x1ffff) >> [ 0.000000] Object 0xffff000010032858 @offset=2136 fp=0xffff0000100328c8 >> [ 0.000000] >> [ 0.000000] Redzone ffff000010032850: cc cc cc cc cc cc cc cc ........ >> [ 0.000000] Object ffff000010032858: cc cc cc cc cc cc cc cc ........ >> [ 0.000000] Redzone ffff000010032860: cc cc cc cc cc cc cc cc ........ >> [ 0.000000] Padding ffff0000100328b4: 00 00 00 00 00 00 00 00 00 00 00 00 ............ >> [ 0.000000] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted 6.11.0-rc3-next-20240814-00004-g61844c55c3f4 #144 >> [ 0.000000] Hardware name: NXP i.MX95 19X19 board (DT) >> [ 0.000000] Call trace: >> [ 0.000000] dump_backtrace+0x90/0xe8 >> [ 0.000000] show_stack+0x18/0x24 >> [ 0.000000] dump_stack_lvl+0x74/0x8c >> [ 0.000000] dump_stack+0x18/0x24 >> [ 0.000000] print_trailer+0x150/0x218 >> [ 0.000000] check_object+0xe4/0x454 >> [ 0.000000] free_to_partial_list+0x2f8/0x5ec >> >> To address the issue, use orig_size to clear the used area. And restore >> the value of orig_size after clear the remaining area. >> >> When CONFIG_SLUB_DEBUG not defined, (get_orig_size()' directly returns >> s->object_size. So when using memset to init the area, the size can simply >> be orig_size, as orig_size returns object_size when CONFIG_SLUB_DEBUG not >> enabled. And orig_size can never be bigger than object_size. >> >> Fixes: 946fa0dbf2d8 ("mm/slub: extend redzone check to extra allocated kmalloc space than requested") > > Thanks for the fix! I missed to test the 'init_on_free' case back then. > > Reviewed-by: Feng Tang By the way Feng, have you noticed the other issue we have, with krealloc() and redzoning? Want to look at that? Thanks. https://lore.kernel.org/all/44fa564b-9c8f-4ac2-bce3-f6d2c99b73b7@suse.cz/ > with one small nit below > >> Signed-off-by: Peng Fan >> --- >> >> RFC->V1: >> Update commit log (Per Hyeonggon) >> Use orig_size to do memset(Per Hyeonggon) >> Add get_orig_size and set_orig_size when CONFIG_SLUB_DEBUG not enabled(kernel test robot) >> https://lore.kernel.org/all/20240819064115.385086-1-peng.fan@oss.nxp.com/ >> >> mm/slub.c | 20 ++++++++++++++++++-- >> 1 file changed, 18 insertions(+), 2 deletions(-) >> >> diff --git a/mm/slub.c b/mm/slub.c >> index 94f5a4143825..a5fbeb2835b1 100644 >> --- a/mm/slub.c >> +++ b/mm/slub.c >> @@ -1895,6 +1895,15 @@ static inline void inc_slabs_node(struct kmem_cache *s, int node, >> static inline void dec_slabs_node(struct kmem_cache *s, int node, >> int objects) {} >> >> +static inline unsigned int get_orig_size(struct kmem_cache *s, void *object) >> +{ >> + return s->object_size; >> +} >> + >> +static inline void set_orig_size(struct kmem_cache *s, void *object, >> + unsigned int orig_size) >> +{} > > Current get_orig_size() and set_orig_size() are protected by > CONFIG_SLUB_DEUG=y macro, and with this patch, they will be called > in both ON and OFF case. Maybe we can just lift those existing > functions out of the "#ifdef CONFIG_SLUB_DEBUG" protection? I agree. As for the "code is larger for !CONFIG_SLUB_DEBUG" concern I think the code will be eliminated anyway, because of the if (!slub_debug_orig_size(s)) return; and slub_debug_orig_size() does kmem_cache_debug_flags() which is a compile-time false for !CONFIG_SLUB_DEBUG. > Thanks, > Feng