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b=Fcw+/5R9kcw8LsyJoA6ElyEpGOjcE2m3FUGmYoCrPJfNrPtwsC4ivvDoGLsTJucS1 AA93jh/leEV2XywhnKRMNbUnT3g1vrn+//65Wd+jTBmYjn1+V0Cr7J3zFHg/YigFRF QUrSNVo/MOAHgb7zeMhe65S2TUsXZw2UXAbolFwY= Date: Mon, 23 Dec 2024 17:25:52 -0800 From: Andrew Morton To: Tetsuo Handa Cc: linux-mm , LKML Subject: Re: [PATCH] mm/util: make memdup_user_nul() similar to memdup_user() Message-Id: <20241223172552.133f4e293f1dfbb6aa86b5ef@linux-foundation.org> In-Reply-To: <014cd694-cc27-4a07-a34a-2ae95d744515@I-love.SAKURA.ne.jp> References: <014cd694-cc27-4a07-a34a-2ae95d744515@I-love.SAKURA.ne.jp> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 9CF234000C X-Rspam-User: X-Stat-Signature: 94d68qjmw9bbf1uhnfj489nwa9fbikzu X-HE-Tag: 1735003525-658489 X-HE-Meta: U2FsdGVkX18h6VvZg/d+C/iv87AViX9a9gzVGV/APkfh2IafsKa6I7qrJ1aN27jfUkLGT6OseBKoOu/iDXa3lLiMcp2WH7Pb3zGDmzIGukZiaPrba+8RPnJLr9PVgJ3/sRWzp0jHnVSvv1E4DR9ajcg6/kW0+zV4HZlgGjA0gfyS0/okDzoy9VwnZ8nNoGvTA13Hyk+GgbZvKM1HcjKB1kXcBPZoaBFsSDg6hyngo/d3Fj/ReDVsR8vi58+D4Tysql1DdC29GxLb7b5xL7fxFf3Inq2HZ+ycFNC6sKh/X2mMetOKxfuT/opUjQ7LHpsBB/5aIyqHCOiVIrbRav21EkSDat+1swDF7a6HVlWMxX0LA95hQMRd4cg32yl/kvtcyGEH24Wyqcv5yIInxTJarxodvKG8eoHiJF8AS65ouThyIc4D2tplxnRrx1RL1gT1b8N3B/uGzhLCHB427MojE3cKPHlNejx2bFU9/TBPVYnnPgDgYpblIAb++k87L9dxgrMPwEKsmqFwXP7XSTMU02QtrgBcdh6SC0UbV0xcZEeXdJjjbyzI8Uey1AA3Gao4L2I8z0dYQEll8fQvhLX+QJGZ6ciUWm+pLcFLhrZRsjxV196Fh5AyY6bB7yoYDODulcA6UmBN2E9nPLSPFJSV5kwQNRqAk5Wez6+dbknswaeUyMGYkk+7lfXaxVZwmSm5s/6Sc6rd7kynsonnwlr6nYIhUuON2kzmcK1SOOJUF7IkmMmuFxBdCvblGl5hmfWh0cOWc/Bq73GKE1A32tzSQjUe52UT9YzqeVe3VWeg2A1rgXnLX7RwNUoPb4cuWNFkItKExrRrko8157dt67QfJX8LGJYxtRYFPRB/kSRgZv/FFdPSTR+UhoQFH2zhIiCi/plPOBua2KxcGQ4HVWHLVZ3frsfjFHP5DzcE5iSI1q0j6FB+ZN+Z/dcCdvgUVEZ89ay3id5PGWiXa11isEA b/mPCVjG 9H/UWu00Fw1cTsxRRb8uLR3Exhn5HSmzUsMBVyOOQtyt674X3q7+1pzYC9BelcP9cr7mZfjXyuvFNLpUvvudPgPQA0QfGitHt5oWV1vYUXQ5pf6Oo9sfruzA4SfydoKVwS89FIHhxFvwnzS4wOa+BvmKRAcm/8Pv4d7mMwPkcwRiPaEXDyjwAkK0+WmoZoSkv/Ttwm7ZtVj+qjMbqa8fYoQi/1VGHuYcUoyuEgO66Cx3Rd+Ty9ZFBQSJSLzXD+t8jlrEJOUj4Vlu/+iB68dvMJhrKP/4+VHj4tS/sSeZ4pPRvYlkI3Gt0lTKt1Tu7V0CEOl2wZFEL4760ANOBStzn5FLTmOe81nuXpTLVbgDFycXHb+P9ISKAxeyFQCmTPBuuxpRXegXE81QqiQBoJKWrwQcwfUGy1whjK/kp 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: tl;dr: patch does three different things, some of which appear to be needed in -stable kernels. On Sat, 21 Dec 2024 16:47:29 +0900 Tetsuo Handa wrote: > Since the string data to copy from userspace is likely less than PAGE_SIZE > bytes, replace GFP_KERNEL with GFP_USER like commit 6c2c97a24f09 > ("memdup_user(): switch to GFP_USER") does Please provide a reason for this change. Does it have user-visible effects? If so, what are they? > and add __GFP_NOWARN like commit > 6c8fcc096be9 ("mm: don't let userspace spam allocations warnings") does. Ditto. > Also, use dedicated slab buckets like commit d73778e4b867 ("mm/util: Use > dedicated slab buckets for memdup_user()") does. Ditto. > Reported-by: syzbot+7e12e97b36154c54414b@syzkaller.appspotmail.com > Closes: https://syzkaller.appspot.com/bug?extid=7e12e97b36154c54414b That's a userspace-triggered WARN, so we'll want to backport the fix into -stable kernels. But we won't necessarly want to backport the other two changes, depending upon what their effects are. In other words, it would be better to present this as a series of three (fully changelogged!) patches, with one or more of them cc:stable. If we really do want to roll all three changes into a single patch and backport that then please let's justify all three backports within the changelog.