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Tue, 19 Nov 2024 20:48:54 +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 bylcGLb5PGdfAQAAD6G6ig (envelope-from ); Tue, 19 Nov 2024 20:48:54 +0000 Message-ID: Date: Tue, 19 Nov 2024 21:48:54 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 6.12.y v2] mm/mmap: fix __mmap_region() error handling in rare merge failure case Content-Language: en-US To: "Liam R. Howlett" , stable@vger.kernel.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Lorenzo Stoakes , Jann Horn , syzbot+bc6bfc25a68b7a020ee1@syzkaller.appspotmail.com References: <20241119175945.2600945-1-Liam.Howlett@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: <20241119175945.2600945-1-Liam.Howlett@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: E0205120024 X-Stat-Signature: akgdjzntapppkq18d3w633yc5rih9xq8 X-Rspam-User: X-HE-Tag: 1732049267-580892 X-HE-Meta: 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 1o70u8zG 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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 11/19/24 18:59, Liam R. Howlett wrote: > From: "Liam R. Howlett" > > The mmap_region() function tries to install a new vma, which requires a > pre-allocation for the maple tree write due to the complex locking > scenarios involved. > > Recent efforts to simplify the error recovery required the relocation of > the preallocation of the maple tree nodes (via vma_iter_prealloc() > calling mas_preallocate()) higher in the function. > > The relocation of the preallocation meant that, if there was a file > associated with the vma and the driver call (mmap_file()) modified the > vma flags, then a new merge of the new vma with existing vmas is > attempted. > > During the attempt to merge the existing vma with the new vma, the vma > iterator is used - the same iterator that would be used for the next > write attempt to the tree. In the event of needing a further allocation > and if the new allocations fails, the vma iterator (and contained maple > state) will cleaned up, including freeing all previous allocations and > will be reset internally. > > Upon returning to the __mmap_region() function, the error is available > in the vma_merge_struct and can be used to detect the -ENOMEM status. > > Hitting an -ENOMEM scenario after the driver callback leaves the system > in a state that undoing the mapping is worse than continuing by dipping > into the reserve. > > A preallocation should be performed in the case of an -ENOMEM and the > allocations were lost during the failure scenario. The __GFP_NOFAIL > flag is used in the allocation to ensure the allocation succeeds after > implicitly telling the driver that the mapping was happening. > > The range is already set in the vma_iter_store() call below, so it is > not necessary and is dropped. > > Reported-by: syzbot+bc6bfc25a68b7a020ee1@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/x/log.txt?x=17b0ace8580000 > Fixes: 5de195060b2e2 ("mm: resolve faulty mmap_region() error path behaviour") > Signed-off-by: Liam R. Howlett > Cc: Lorenzo Stoakes > Cc: Vlastimil Babka > Cc: Jann Horn > Cc: Reviewed-by: Vlastimil Babka