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t=1793186731; bh=YKaulhQLxUfKWnBASX1S/dUGhwJrFBUH8NuOouts5+I=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=P2hok/IQmwm8cB2bnDnrDcPeAaV73twbAWps9caSEi5dY2Jcd844rTaNBr92pszip d/LDigAE/b9OTh414eXiZq1JnhVYqaRVz2PyIEus6hbpQG3OwnnX2NsX+NjmIMCxx+ FVgww7zQ2JJU5HdwtOCk7+2L5pU8iAEcRnD9k6Qc= Message-ID: Date: Wed, 28 Oct 2026 16:55:23 +0530 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 6/7] selftests/mm: check MADV_PAGEOUT file permissions To: "Gregory Price (Meta)" , linux-kselftest@vger.kernel.org Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, shuah@kernel.org References: <20261019171206.3331374-1-gourry@gourry.net> <20261019171206.3331374-7-gourry@gourry.net> From: Sarthak Sharma Content-Language: en-US In-Reply-To: <20261019171206.3331374-7-gourry@gourry.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 12ED8A0005 X-Stat-Signature: tigehs3dm1x7eun5fn9yfuuy9azsy38d X-Rspam-User: X-Spam-Status: No, score=-12.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1793186731-576734 X-HE-Meta: U2FsdGVkX1/r58xAt0h2BC1HdrwPpdq159tPMUsnWIpJgK0dBlcGCAQ1tnZJo4mR4f92fcOMVmNfFShIl74E+G8IAk2blSTMyVJLCrTTzDf5+o9ne/Mui0/LYyISBa4vNm5WArvI6/jSO0L3OooNHHzefNdek+2YpY+ojLJrwcpmdnevVZ3Cz63juiwymR2E21lxFfIMYeZfGcLpvrC+3XOIt4h9o3JM/KxmxKU91iQeLEkXncotZ8fAR2v9Q6dm1jg3bcOI8YkR+u79kuc6htl8X3LtAAATiwO5C9ANxhEwwrRP+nfgZK9CD/mhhdNeUUpmbyX0mTXZvDfkgrwpbmvlH3zW+R7oC4WYzsW4j+D2Anxq0ngXQCxmaErdtlMwJrDsIdxQioSTALAaLedMZoMupNuyzLo2cRnnbjjVn1xH2LxR8leyV5+06W9k9GRxN0BNrdZXywX4D4SjF15Pm+IoDvawutT1WMLZjAzZrl9k5/5s2rC/inG0poppujpSw9U82cifBNsR10noBA4nVg9JOtMgNiPA/WPzDJipxd8KiU52rLBDlTPHDLtfIurIFCaKlSQH5F/vFL5FazFVPfsjxq7Aj7k64VFQdz7lnbWxWr2qE92PLel57502FC6vKgw+plTA+bIdQfPT3LPm6MlEgxrBTcCHM3ubNLjpRvh53a97BBbJ2pi47O6nE2wpKbBQQ1e1WpTMgSVQYUdjEpk9Hf3wnQo4MqddoAkaRK0T5wsDN4o9UG1aiFrZ+M+aCiRiHMMQpEJmI0PDJf46/d1IdNutCv4zcfsnBIyHWPlPLKIJhLgpBaiwdEYRZjkRBfrX2SJE2q+a4/nBvUmEpX2CFvcPtP3NBjmYRXQW+SxkNaCISznIwjchdmSaj/X+TtpRlYQb8NIRYwhYfGQrnqceEwkgg5saQKZHF60wDE7luer9T6UIG3PCEU5jjnBWUjOGQ3vv5OfMjQTkJUP oN7WG+7v 4E6qLA1m/4AI82NfGYYEdqhVUNDjex/7Su8M3kTmBLjkcFei62orsPk7wpw7iUT/Q6ZDlRz9mpHO7aTAFaceomqXgUbjvWn8VSYxwGBHCXlt1tABTJXNMa0DKHDEyKBWODcjAtb+LBAxMBnG4ay6pzQnofu87XMeGIVAYPm5wdiA7Btt6UzaYq3zNXW4+XsvjwiEfP7N6L8FJpGCDYzkFMp7i2qn1hdds2z1MaxGIs/TlpkROTPHAnFuJQ///nrvXB9l2UQ2iRM9BjcL6cmEXvIV1UroQqZ6HnDEReH1LIpnkXPo1FIk7rVB2LwDUw3nh6gEd7DoYQcBgEkcpMiQPXNkWHK3kDv+hiChPAUqQklU/O6pJRH+CR1JGL58pHaKPEnhe2F/8HQ3gAcQlvMuSLT8M0w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 10/19/26 10:42 PM, Gregory Price (Meta) wrote: > MADV_PAGEOUT only pages out file pages for a caller that owns the file or > could open it for writing, per can_do_file_pageout(). Any other caller > gets nothing from a shared file mapping, and only the anonymous COW pages > from a private one. > > main() now also checks once whether MADV_PAGEOUT can unmap a clean page > of a file in /tmp, where the tests make their files. The tests below skip > if it cannot, since none of them would show anything. > > Check that the owner of a read-only file can page out a clean page of > it. When started as root, the test hands the file to nobody and drops > privileges, so that capabilities cannot stand in for ownership and > nobody need not be able to write to /tmp. > > Also check that an unauthorized caller leaves a shared file page mapped, > and that it pages out the COW page of a private mapping but not the file > page next to it. These need root to change credentials, and skip if that > fails. The private mapping check also skips if MADV_PAGEOUT cannot swap. > > Signed-off-by: Gregory Price (Meta) > --- Thanks for the changes. It looks good to me. Reviewed-by: Sarthak Sharma