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Tue, 30 Jul 2024 21:14:16 +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 oYbpF6hXqWYlWQAAD6G6ig (envelope-from ); Tue, 30 Jul 2024 21:14:16 +0000 Message-ID: <66836dd6-b0c2-4f77-b2a3-c43296aa6c93@suse.cz> Date: Tue, 30 Jul 2024 23:14:16 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] mm: krealloc: consider spare memory for __GFP_ZERO Content-Language: en-US To: Danilo Krummrich , akpm@linux-foundation.org, cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, roman.gushchin@linux.dev, 42.hyeyoo@gmail.com Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kasan-dev References: <20240730194214.31483-1-dakr@kernel.org> 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: <20240730194214.31483-1-dakr@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 58B3A4001B X-Stat-Signature: 4iin1wpmuwusun5i1nkjadphx6dfbfj7 X-HE-Tag: 1722374058-980653 X-HE-Meta: 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 QIAgT9uy A77UiCV7AOswGr/ObUa+bxfjUX6lsUkbs2lEgGmH6WxuzQxr7laE3UYjiA7ZztzDIzH2UnNbIvJKQ1c9e9W0ut9SvzyAuqDrvJjEQSvB7jUjVO0W/j7ZmTFnaQAk8iOdoK5Z40isKgM/FxjqQPPt46ZVdkOWXrqPx35Wm9GHHxmJhPTNJCIK5ZQFUeTEdw4JwrcyEwsDHa1tqMoXJnDPl3YANCN7G+0con+N2WJka5EPtb5sNXGbOAxeKqusWExG6TQA0UKVivBJhoVu3bkr6jXt9wn2IEPwEnYjGXcc4HfvasphSy01dtMKSNQZxbsqUmtecsGEru5zHiqgxP8iYMjXkuwjQt9jKYnIqZwSM17fnwDZeyHu4uPCVKU5+IbLgI7U0f3xe6xeDVnhbPCHZkKB75b6YaGutgAeSEojQJkeSiHcDDqNp6HIoVg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000002, 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 7/30/24 9:42 PM, Danilo Krummrich wrote: > As long as krealloc() is called with __GFP_ZERO consistently, starting > with the initial memory allocation, __GFP_ZERO should be fully honored. > > However, if for an existing allocation krealloc() is called with a > decreased size, it is not ensured that the spare portion the allocation > is zeroed. Thus, if krealloc() is subsequently called with a larger size > again, __GFP_ZERO can't be fully honored, since we don't know the > previous size, but only the bucket size. > > Example: > > buf = kzalloc(64, GFP_KERNEL); > memset(buf, 0xff, 64); > > buf = krealloc(buf, 48, GFP_KERNEL | __GFP_ZERO); > > /* After this call the last 16 bytes are still 0xff. */ > buf = krealloc(buf, 64, GFP_KERNEL | __GFP_ZERO); > > Fix this, by explicitly setting spare memory to zero, when shrinking an > allocation with __GFP_ZERO flag set or init_on_alloc enabled. > > Signed-off-by: Danilo Krummrich > --- > mm/slab_common.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/mm/slab_common.c b/mm/slab_common.c > index 40b582a014b8..cff602cedf8e 100644 > --- a/mm/slab_common.c > +++ b/mm/slab_common.c > @@ -1273,6 +1273,13 @@ __do_krealloc(const void *p, size_t new_size, gfp_t flags) > > /* If the object still fits, repoison it precisely. */ > if (ks >= new_size) { > + /* Zero out spare memory. */ > + if (want_init_on_alloc(flags)) { > + kasan_disable_current(); > + memset((void *)p + new_size, 0, ks - new_size); > + kasan_enable_current(); If we do kasan_krealloc() first, shouldn't the memset then be legal afterwards without the disable/enable dance? > + } > + > p = kasan_krealloc((void *)p, new_size, flags); > return (void *)p; > } > > base-commit: 7c3dd6d99f2df6a9d7944ee8505b195ba51c9b68