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Tue, 18 Feb 2025 14:15:11 +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 HLAzGe+VtGenXQAAD6G6ig (envelope-from ); Tue, 18 Feb 2025 14:15:11 +0000 Message-ID: Date: Tue, 18 Feb 2025 15:15:11 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/4] mm: allow guard regions in file-backed and read-only mappings Content-Language: en-US To: Lorenzo Stoakes , Andrew Morton Cc: Suren Baghdasaryan , "Liam R . Howlett" , Matthew Wilcox , "Paul E . McKenney" , Jann Horn , David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Shuah Khan , linux-kselftest@vger.kernel.org, linux-api@vger.kernel.org, John Hubbard , Juan Yescas , Kalesh Singh References: 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-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 512AD100010 X-Stat-Signature: gyftcpteyz4w9rebam1ro8mben4dcqd1 X-HE-Tag: 1739888113-467741 X-HE-Meta: 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 NsPQvMG+ 9rGGbNc4igygyAvRS5VhvTDupyE7WodUAj5TacTUVK0hdUknjIqlVai6xwpTPsVZmStZmDQyj2p4dLca0ERMsXNZ//2+N1LX3km7+PYF0759Iq4e3DZrrmDjI2yXkkrJyeHKeLQJgz8eMiOtITtjfU+OAfRYHuNzOVQ/vswMBjoI9aYjoIhidHah4k8n4xYJ9inIqC0rP+nMYQX7Ojo2vbTvjIEl0npdyoJDC9vlGNKZLLwzUyj1B50TcgdlISltjteTbr+aIv4dr4X7FsszoNv6+1GqIdw2mvpbW1CnfmGJsNFoody6QMcJuoA== 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 2/13/25 19:17, Lorenzo Stoakes wrote: > There is no reason to disallow guard regions in file-backed mappings - > readahead and fault-around both function correctly in the presence of PTE > markers, equally other operations relating to memory-mapped files function > correctly. > > Additionally, read-only mappings if introducing guard-regions, only > restrict the mapping further, which means there is no violation of any > access rights by permitting this to be so. > > Removing this restriction allows for read-only mapped files (such as > executable files) correctly which would otherwise not be permitted. > > Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka > --- > mm/madvise.c | 8 +------- > 1 file changed, 1 insertion(+), 7 deletions(-) > > diff --git a/mm/madvise.c b/mm/madvise.c > index 6ecead476a80..e01e93e179a8 100644 > --- a/mm/madvise.c > +++ b/mm/madvise.c > @@ -1051,13 +1051,7 @@ static bool is_valid_guard_vma(struct vm_area_struct *vma, bool allow_locked) > if (!allow_locked) > disallowed |= VM_LOCKED; > > - if (!vma_is_anonymous(vma)) > - return false; > - > - if ((vma->vm_flags & (VM_MAYWRITE | disallowed)) != VM_MAYWRITE) > - return false; > - > - return true; > + return !(vma->vm_flags & disallowed); > } > > static bool is_guard_pte_marker(pte_t ptent)