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Tue, 1 Oct 2024 16:42:48 +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 I5ybB4gm/GbVSgAAD6G6ig (envelope-from ); Tue, 01 Oct 2024 16:42:48 +0000 Message-ID: <84837835-b483-4d15-9e0f-1719c350423e@suse.cz> Date: Tue, 1 Oct 2024 18:42:47 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH hotfix 6.12] mm/mmap: correct error handling in mmap_region() Content-Language: en-US To: Lorenzo Stoakes , Andrew Morton Cc: "Liam R . Howlett" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Bert Karwatzki , Vegard Nossum References: <20241001133726.160275-1-lorenzo.stoakes@oracle.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: <20241001133726.160275-1-lorenzo.stoakes@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: DD7DA180006 X-Stat-Signature: ssg9kjgmdwgdn6t73oh7ewuiwp7cxk7c X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1727800969-983001 X-HE-Meta: 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 8txOXkw8 gCAVw80XqJecWg3eNSFJ2u/eZNRJpl3ApBiPGmNiZ+ddmMZoVdnvTKvkoZwvBMI+QoLIsAXKPlJhS3zDGspfEG57Rk1ot/xmBLoKnV55EikBXQ5IP4F3lYEsCp1Xhe/29aGKsYlXb+a4w8Br6GEC4rXp3K59wKVb3fNxPQmhqrvzGFn6HsGoq82UJgs6yBZeau/L/zLqe2Z7WIdrxIWali63pDsh1TBrsGBBJYPBnyMCc/di1k1GJlYBz7euK+6v+QUioaJQUsJazfhuFZsMtcbezR8HJv3wFfhPqTNshPhbmpMm8OjF+pai2U/5i6iSjPb8lgVaoTVralTkgGZumBpRO4eApktdrBcUriSTSVY8HfLGOFMVo3qg/tryxhD7n849C 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 15:37, Lorenzo Stoakes wrote: > Commit f8d112a4e657 ("mm/mmap: avoid zeroing vma tree in mmap_region()") > changed how error handling is performed in mmap_region(). > > The error value defaults to -ENOMEM, but then gets reassigned immediately > to the result of vms_gather_munmap_vmas() if we are performing a MAP_FIXED > mapping over existing VMAs (and thus unmapping them). > > This overwrites the error value, potentially clearing it. > > After this, we invoke may_expand_vm() and possibly vm_area_alloc(), and > check to see if they failed. If they do so, then we perform error-handling > logic, but importantly, we do NOT update the error code. > > This means that, if vms_gather_munmap_vmas() succeeds, but one of these > calls does not, the function will return indicating no error, but rather an > address value of zero, which is entirely incorrect. > > Correct this and avoid future confusion by strictly setting error on each > and every occasion we jump to the error handling logic, and set the error > code immediately prior to doing so. > > This way we can see at a glance that the error code is always correct. > > Many thanks to Vegard Nossum who spotted this issue in discussion around > this problem. > > Reported-by: Bert Karwatzki > Link: https://lore.kernel.org/all/20241001023402.3374-1-spasswolf@web.de/ I'd be surprised if that fixed the reported issue, but yeah this is a bug to fix anyway. > Suggested-by: Vegard Nossum > Fixes: f8d112a4e657 ("mm/mmap: avoid zeroing vma tree in mmap_region()") > Signed-off-by: Lorenzo Stoakes Reviewed-by: Vlastimil Babka