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b=PoYMuCbD9oC73v8MabIRDQ3JYH4XeiHnm5aaAnrfKac+pcFVw4u0zG7Q5mO/e9wxlyeOe1 wPCpRD4zwp1eT+md7c3/W0aYzOGHlnT6XAd34OlyX3hv644M2SrlvG9My5h0E0JjR/haAm ybqfvaacyuI66Ycljs6YAwFwuRtx0CHUVbs9OxdIiRyxGfXNdfcsrWzVw19u+VGcM8FNWY Im0iNN6j6OH7JGsKriu7qK96ggrORz8IKbl/de/VP6+UJsZ1LQ5eAIWIK96cIou9vZpJ7X 62BWFHiHBNxIWrUKhHUP5AY/PpCAmhqqKAFZ0q7bndsF8kef3Gww0bAYOPxKFQ== Received: from localhost (gaia.codewreck.org [local]) by gaia.codewreck.org (OpenSMTPD) with ESMTPA id 02e7d134; Tue, 22 Sep 2026 08:45:29 +0000 (UTC) Date: Tue, 22 Sep 2026 17:45:14 +0900 From: Dominique Martinet To: Andrew Morton Cc: syzbot , apopple@nvidia.com, byungchul@sk.com, david@kernel.org, gourry@gourry.net, joshua.hahnjy@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, matthew.brost@intel.com, rakie.kim@sk.com, syzkaller-bugs@googlegroups.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, Eric Van Hensbergen , Latchesar Ionkov , Christian Schoenebeck , v9fs@lists.linux.dev, Nguyen Ngoc Thang Subject: Re: [syzbot] [mm?] WARNING in v9fs_fid_get_acl (2) Message-ID: References: <6aae188b.71f81b7d.15fa6d.0004.GAE@google.com> <20260919031451.3f47a8da8405e88fa1ab5398@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260919031451.3f47a8da8405e88fa1ab5398@linux-foundation.org> X-Stat-Signature: rxp7kmhj8djogr4fjyx6muqp4ryow7g4 X-Rspam-User: X-Rspamd-Queue-Id: 2616B40008 X-Rspamd-Server: rspam03 X-HE-Tag: 1790066739-252832 X-HE-Meta: U2FsdGVkX19AIKQgK/EXE7pAK6umEJEVkfg8pabTVfjqXvIzuvYpiACENufH7tjfDAXxsKwnYyxi2gPaIXcla7xVjzJdOpKR2Nn6bGArUB6tYGDRH5xp/I4VCsQRv9/kE4VNzF4zosfhutB9+m8rKp+I8OKVSLzBDouZiWJAKTCqRnPkh+G/XjndX4RLPeUZRsYayOB/i7VIBNZ7KMSGXHnhpddkARdzbp/21Q8jhpqhDkVPHq1/tGOxIFXQjfBiHJzz14Lua4sYRgyDXhdkqAP0rLfzA6ACqwaz1F5JKAsDIU4DLwV2pkhB9T78gv+6maf5JDhyrB/n7bjNx3jLVIlZ47Y1xMLYTfEYdrULD1hYelFlZP+hHdmRlQJuSV0EaU4ErVRAXO89Okwx9btYGfDlMy3NBsIhTGksDHJCErQD63XyvW0zVi4h9qhWkku1hpcZ0tn567Kk5/xV+F+3KVP3ppHtgFReAVR3K4+oH2SF+8zf0F7h8WRLimiH5SU0NWRf5dZJLsN+M18XUYjjp9trpuKkzZeeznlO4uW5FEijoSaQwmHLnPLBHsevvifLJEU1IBuotDReGKOlCeYiLF1rudEpNRIszHS5nTE6QIMh2rtXltKVUnV6d1FyzqJX61KX9fjjRlnjKdwX1ezWUnX0CP7TgVLTmj7mb+YEp7HKey6AHmmUrBd9V82o2Lj5sCyurwvnPb0IGic/TwCO2Gf3KSVne9e8oPs2x1TP5/7gqWYRY6GCcrAg1iQaHDnuQU5anTCXFyMJ40lbYaBCkA11m9AcHAN838myJmwcPhYFbIIPS1uyrOfBNEAf+yq4V8XdWe9SxPECjn4Z1fyiCoQdJnRm20yxe65kuNRmns20RLHWhQd+mVKtikaBf8wB8uL8RbxAFNDxBg2r4r/fsd+ocKr37iBH2rrMByG4OObiuBNYSQdpYrmLJCxmN5RUtF8BxQ99ITzZeDJiP6y 7+pmpkTy 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: (+Nguyen in Cc as he tried resending sloppy patches after this) Andrew Morton wrote on Sat, Sep 19, 2026 at 03:14:51AM -0700: > > WARNING: mm/page_alloc.c:5340 at alloc_order_allowed mm/page_alloc.c:5340 [inline], CPU#0: syz.1.357/7872 > > WARNING: mm/page_alloc.c:5340 at __alloc_frozen_pages_noprof+0x2137/0x3300 mm/page_alloc.c:5397, CPU#0: syz.1.357/7872 > > Thanks. Caused by an old v9fs bug. A fix was proposed but never merged: > https://lists.openwall.net/linux-kernel/2024/02/02/806?utm_source=chatgpt.com Right, we've been going in circle with this since forever, and nobody answered Christian Schoenebeck's question[1] about what the limit should be, and while I don't care much ultimately I sort of agree with him (e.g. limit should be XATTR_SIZE_MAX for anything that the VFS layer touches, but acl are converted within the 9p subsystem and could be arbitrarily large so status quo of a KMALLOC_MAX_SIZE limit because they could come from something else) Andrew, if you have an opinion on whether we should cap the acl sizes anyway, please say... [1] https://lore.kernel.org/all/Z1n-Ue19Pa_AWVu0@codewreck.org/T/#md7c1e009696501b3b87940cb613150bdebd1db28 -- Dominique Martinet | Asmadeus