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b=Q1Cb6XZ+yCNE2dqg4oFZEsejxSK8qmDhJ9qEH5U7kwG8exMHtomAVngfn84FHrpiH Crue1/GAN6blJk/5iWA0EyUN4+zwWK7l9ZaE2iviSXNO1pU6jVvMlDj8HFiQVsEE7s 0L5eRAmhabTPpZEYzkJ2DxTDPxpK1pp7wqHs2vK8MayT5Dg2wSuGdvH85xwnyezDzO vJLGqcJ4nNuaINUFqjMIePNLCJ7Aou43z48qi1MYqYYJv80pwmEcD21V92fBrGXW2+ AO1sE55E4Qx5izoy0MhsiIkBDxq5457H5ScKxqNzcQ+kq/TpgFNkJ2iFYrDjc09OzI SJm5eJpnOhkxQ== Message-ID: Date: Thu, 15 Oct 2026 18:47:14 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/slub: initialize the free pointer of the bootstrap kmem_cache_node Content-Language: en-US To: Karl Mehltretter , Harry Yoo , Andrew Morton Cc: Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Shengming Hu , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20261010203906.93156-1-kmehltretter@gmail.com> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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 BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSNWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBrZXJuZWwub3JnPsLBsAQTAQoAWhYhBKlA1DSZLC6OmRA9UCJPp+fM gqZkBQJqFFy6GxSAAAAAAAQADm1hbnUyLDIuNSsxLjEyLDIsMgIbAwUJGtCBUAULCQgHAwUV CgkICwUWAgMBAAIeBQIXgAAKCRAiT6fnzIKmZJIUEADFx/tREzUImHrEwVHeSvDFmA7tJysI UVrlvrM09E7GIuzphzv7jYmo8n3ANpCczLEVr4G0syYQdTigaZgv3+FQDIIzhKih1IHhu1Ei XHlywNWKnQxxQEUNi5Mwx43wQz5XVw9F1A7gtKBKNtfogO511hAbrzagrYajyQacEJ/+sfhZ 9Da8ltHIXD8pcYaHUfQgEusCgmEd9+KrUwrTbckFKmYq5chuE6yJ4J0EmWknL096jIE6CnzF FRslQ3B1UKDjxVsm1ZHfir5NeWszLkTvGFsddFaWTgh8UycESG6VQzKXjjewXu2pG7YQYRpj QKm1W5X2TkwWkXRBZTmfmbhxIUMh3+zf5wQ463rSmDN/8v81tdqBtAW6rH/kzg1GvkaTHXn0 507yEHFzBksk2viAuIxxr7km8+/KARYLIdGtx30EG8cKzAUZOK6WqxtNCsXUJNrVE8CWrCaD icoNu7Fs1c5hmPHdSTnU48ce67449DdnO4neLSNhRiGlMHJgfJUmgrxu/hcYeOZ3haWmEQ2w uW1Mh01OHi8QZHCEyAbABrPs9GUgccc/4eYXX9hIgxfSkYzn8f+8NuIFPWl/0uTvjgqU29FQ SbzOLxHq9439Ox40G5mS5eZXRGxITYR+6TXvRGI6P/264jvflnr/pDGUttaikU+0W+1uxgKH cmYbEc7ATQRbGTU1AQgAn0H6UrFiWcovkh6EXVcl+SeqyO6JHOPm+e9Wu0Vw+VIUvXZVUVVQ La1PQDUi6j00ChlcR66g9/V0sPIcSutacPKfdKYOBvzd4rlhL8rfrdEsQw5ApZxrA8kYZVMh FmBRKAa6wos25moTlMKpCWzTH84+WO5+ziCTsTUZASAToz3RdunTD+vQcHj0GqNTPAHK63sf bAB2I0BslZkXkY1RLb/YhuA6E7JyEd2pilZOrIuBGl/5q2qSakgnAVFWFBR/DO27JuAksYnq +aH8vI0xGvwn75KqSk4UzAkDzWSmO4ZHuahKtQgZNsMYV+PGayRBX9b9zbldzopoLBdqHc4n jQARAQABwsF8BBgBCgAmAhsMFiEEqUDUNJksLo6ZED1QIk+n58yCpmQFAmfIHFQFCRYU6J8A CgkQIk+n58yCpmS2PA//bqN1LfcotmArgElsa+0EGZSQlYgK48pm8WAeTXTngudP9IJ4SuKY HR5RNjHcBeqN+Me0zxRqYzRb8nGanHEkDyf4Im8DQM8d6vbyU+FcPmG4skud4kgS1zMHnlVd SXfSIwKC/hKgdHG8aBV7545Lz9X6Iohea+94wneD0aw/hqF+QWewGZhWJriWAZtvEkzNjQOi 4U9F/trLten/x7bpphDSnDMKJtITbtzATT1Dq7o7VpIUK1nCTQALMuMjKCdi8OdU/+V+R3O4 0PXWvX8qrvqYapVbZ+9KqT74FsuB0Ya9uXwgBF2Q6cRuETZk5vqaqKxzqoQZCO8AOz/58j6O 2RHNy/mZEN+7tJ5Tsq42zVJ4jxsT8b9YplavCMsnBgDeRWhcbYhCyttoL7nYISyWg4kQYZ/P wIV3OuNv2f8iKYsxNsRuClOAF82+gvqOy1/1pprFjy8uo2pkoOrb63aOP3vO5VHnRKgra6dq NcaZ+c6J4H+nEJGi2SkHAUJz5oBzuThvPudLvPA/SK8sKoM01IRxSihev/S/5WLazXB1PGem OCbvzC1IjWJJraxiDJ5IygokapUa2RP7+WBR22skQ3SSl6G107QgWKSyTOGWEaRmV53vxQLV jXuCmzSSasTL60zq5yGrT4/DYQVSNEUiUbG4pYekxJujNeEDkUlky0Y= In-Reply-To: <20261010203906.93156-1-kmehltretter@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 7E4F2C0003 X-Stat-Signature: 9jhkzzm5zwiwyz41akjkurk8ycya66gn X-HE-Tag: 1792082839-196442 X-HE-Meta: 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 8I5mLocV bzJWN/K7K0FunXzbQPgKmIyVnsHxsOcX4Gw90h5PG22p9c/iotB1mtTt/kds5505nOIKjuT3ZxEG+Ga79ubfQkZt76ylftYM0CeExXOtq+jXHIdt6JRfNz7aDhnwVZT+aGWaicg1kXi0tVqtmZYEAupea2eQWrm/CAH2xkQmCkYNt2VlQBe8xD4BeuyuDiYGbdt+xsWc9MiGscXwqaQ26vL6zs1WUC1pXKcV6juqJqMLFYg05nMePOx8zJndAhc0C8pvc6Dr1eOoMF/6i6o7iHpM0rlhVtpn/pwKkD/rP95Cp3efcB0qoWIdhSD/efK076TzVlBO5L94Il4m5/gQjCn3rJvKqie+ukksw Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 10/10/26 22:39, Karl Mehltretter wrote: > With slub_debug=FZPU, validating kmem_cache_node reports > > BUG kmem_cache_node (Not tainted): Freepointer corrupt > Object 0xffff888000140040 @offset=64 fp=0x5a5a5a5a5a5a5a5a > > and taints the kernel. Poisoning places the bootstrap object's free > pointer outside the object, where check_object() checks it even while > allocated. > > early_kmem_cache_node_alloc() previously took this object from a > freelist with an initialized pointer. It now takes it from the slab > iterator and builds the freelist only for the remaining objects, > leaving its pointer filled with POISON_INUSE. > > Initialize the bootstrap object's free pointer to NULL. > > Fixes: dc795d4c0282 ("mm/slub: defer freelist construction until after bulk allocation from a new slab") > Assisted-by: LLM > Signed-off-by: Karl Mehltretter Reviewed-by: Vlastimil Babka (SUSE) > --- > QEMU x86_64 and custom QEMU SH7785LCR model, slub_debug=FZPU: > validation reports "Freepointer corrupt" before the fix, clean after. > > mm/slub.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/slub.c b/mm/slub.c > index 54ec125033571..9a20aa820bb0f 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -7777,6 +7777,7 @@ static void early_kmem_cache_node_alloc(int node) > > n = next_slab_obj(kmem_cache_node, &iter); > BUG_ON(!n); > + set_freepointer(kmem_cache_node, n, NULL); > > slab->inuse = 1; > build_slab_freelist(kmem_cache_node, slab, &iter);