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b=eN1lj5qOb5fu9EekeSPmrWTJxEQfkM8wW3zTNJHj/Vv6cKTUnD5S1jnm78DMubUyK s/ZcljVOmAQzh/i1NiYTQbwrmjxhyhCTWKTciw0i/lKBO421kKUa8z4C4OC4JitIdv +qrL5lwnVFpp1jwQI9e3WM/rPG456maWGLFt4DcQP1wpihsBchKaw93MAz3YfkXTRV z0w1J2HP7Rl5Pl0BxMG/50TKxMMFXbFVqkD1bQsux9y1PP99PjEefKStxS9NpcmmW7 xq5yv2KeN8lLQkfwDBpW5X59DigYTfawEerDvRtxWGAIxTRnF+xccwrrEs4EyjwwOF aq006WL96a4eA== Message-ID: <73d28cff-77f5-4cd6-888e-5dce5ebae459@kernel.org> Date: Thu, 30 Jul 2026 16:15:26 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] slub: print just the function name in /sys/kernel/slab/*/ctor Content-Language: en-US To: Harry Yoo , Alexey Dobriyan , Andrew Morton Cc: Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , linux-mm@kvack.org References: <456c0a37-9074-45b5-9be2-a5f2fe345400@p183> 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: E51674000A X-Stat-Signature: rm485rpqaobyewunzskrjf6d6hb13y6x X-Rspam-User: X-HE-Tag: 1785420930-338379 X-HE-Meta: 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 CVh1ecMV zv2vJXCAAKzDsAeiZY4LFtykrsBNU8x0L50C6P5j8UkmOUWzUQEZGeNkDe/jNXDlDxJic/S7j7VCSVn7GHC2cXC7ZabOuGnc22Fe5DhIQ/t37hWoWmn6PeyAdCPWJTJMEzu/BEXmpDYhSroTyDoeZfg095dFjeApJdl4mR8hfWRPmprOpernA4Gh5WEJPi9s2myeuyKAL8J3yfIOxixGbZE2xqXA/u+fbFH5SCdIDv2kC9uYiXXw0HqsgXm4CHqGexU7nwUI6bT5B9QdkjoaSXZ8tEQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/27/26 07:27, Harry Yoo wrote: > > > On 7/25/26 10:28 PM, Alexey Dobriyan wrote: >> Sysfs "ctor" file prints offset/length of the cache's ctor function >> >> $ sudo cat /sys/kernel/slab/bdev_cache/ctor >> init_once+0x0/0x10 >> >> This is not useful: >> >> Offset will always be 0 because ctor is a function. >> >> I'm not sure what ctor function size is doing here, it should be in >> /proc/kallsyms >> >> Signed-off-by: Alexey Dobriyan >> --- > > I'm not convinced that changing this (without strong justification) > after exposing it to sysfs for 10+ years is worth the trouble. Agreed. It's a pity this was exported in the first place. I can't see a benefit for anyone knowing what the function is called. Should have been at most a flag whether there's ctor or not. But possibly a justification is not to leak the function size, which might be theoretically (although unlikely) a hint to some attack. Well at least if somebody complains about getting broken, it's trivial to revert and we can hear about their usecase. In-tree tools (slabinfo etc) were checked to work properly? >> mm/slub.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> --- a/mm/slub.c >> +++ b/mm/slub.c >> @@ -9149,7 +9149,7 @@ static ssize_t ctor_show(struct kmem_cache *s, char *buf) >> { >> if (!s->ctor) >> return 0; >> - return sysfs_emit(buf, "%pS\n", s->ctor); >> + return sysfs_emit(buf, "%ps\n", s->ctor); >> } >> SLAB_ATTR_RO(ctor); >> >