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Wed, 31 Jul 2024 14:31:14 +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 Ye3lLbJKqmYKdQAAD6G6ig (envelope-from ); Wed, 31 Jul 2024 14:31:14 +0000 Message-ID: <17d83377-4904-49a3-9b3e-2ea0aefd9885@suse.cz> Date: Wed, 31 Jul 2024 16:31:14 +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 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-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 7FA2B180040 X-Stat-Signature: zaqu8w18pqgy81jfdmjhxfz14j7e6n9a X-Rspam-User: X-HE-Tag: 1722436276-976426 X-HE-Meta: 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 vRoIedLH FekR+JjeoliV+fxO9LSFGMpBT0FDrEv3BgoZu2up9qCLB4FAZ46YqnmHGp+xfPmHvVt0J4MccQSzXH3keKnJRYfgCW/dQrti/k9qoBZYcMKWgsLfn3pBUTqoxnSMu0wfEjF5NCsDV1YH9Q8J1ShsuP+1VSd1/jFPdTClFfjquSASNJFf3hFmVQ8HVCr/tJUud2p9OsJrANSP3DPl67LYJxz+gNJdlEMFLotvuiA6t5k+OlJ750jPTit39G8RIOgCEdmNVuVbGiSzjwHejK3g9ki+xoFwzO8OfXXwtHc9o2S1zh6thKURVtWmqIN8Huv+1G5ziYPXzugyDrlgJdRtq6zl1qwcyFh3PeEyKs/6XrNlHHKM7Qd1S0UDnbnJ28/6sKKCw7OuLUyCp8b47PzeYHL11W1/dwX6CpDfDvvSc/JJU3TRhtAFz6Lkleg== 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 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 Acked-by: Vlastimil Babka > --- > 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(); > + } > + > p = kasan_krealloc((void *)p, new_size, flags); > return (void *)p; > } > > base-commit: 7c3dd6d99f2df6a9d7944ee8505b195ba51c9b68