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dkim=pass header.d=google.com header.s=20210112 header.b=Zz5NixJh; spf=pass (imf09.hostedemail.com: domain of elver@google.com designates 209.85.219.174 as permitted sender) smtp.mailfrom=elver@google.com; dmarc=pass (policy=reject) header.from=google.com X-Rspamd-Server: rspam02 X-Stat-Signature: y3rnsgfpoxxkg8tsekay8zyur4cwgrcq X-Rspamd-Queue-Id: BCF90140030 X-HE-Tag: 1656401174-569687 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: On Tue, 28 Jun 2022 at 08:41, Yee Lee wrote: > > On Fri, 2022-06-24 at 10:28 +0200, Marco Elver wrote: > > On Fri, 24 Jun 2022 at 10:20, 'Yee Lee' via kasan-dev > wrote: > > > On Thu, 2022-06-23 at 13:59 +0200, Marco Elver wrote: > > On Thu, 23 Jun 2022 at 13:20, yee.lee via kasan-dev > wrote: > > > From: Yee Lee > > Use MEMBLOCK_ALLOC_NOLEAKTRACE to skip kmemleak registration when > the kfence pool is allocated from memblock. And the kmemleak_free > later can be removed too. > > > Is this purely meant to be a cleanup and non-functional change? > > Signed-off-by: Yee Lee > > --- > mm/kfence/core.c | 18 ++++++++---------- > 1 file changed, 8 insertions(+), 10 deletions(-) > > diff --git a/mm/kfence/core.c b/mm/kfence/core.c > index 4e7cd4c8e687..0d33d83f5244 100644 > --- a/mm/kfence/core.c > +++ b/mm/kfence/core.c > @@ -600,14 +600,6 @@ static unsigned long kfence_init_pool(void) > addr += 2 * PAGE_SIZE; > } > > - /* > - * The pool is live and will never be deallocated from this > point on. > - * Remove the pool object from the kmemleak object tree, as > it would > - * otherwise overlap with allocations returned by > kfence_alloc(), which > - * are registered with kmemleak through the slab post-alloc > hook. > - */ > - kmemleak_free(__kfence_pool); > > > This appears to only be a non-functional change if the pool is > allocated early. If the pool is allocated late using page-alloc, then > there'll not be a kmemleak_free() on that memory and we'll have the > same problem. > > > Do you mean the kzalloc(slab_is_available) in memblock_allc()? That > implies that MEMBLOCK_ALLOC_NOLEAKTRACE has no guarantee skipping > kmemleak_alloc from this. (Maybe add it?) > > > No, if KFENCE is initialized through kfence_init_late() -> > kfence_init_pool_late() -> kfence_init_pool(). > > Thanks for the information. > > But as I known, page-alloc does not request kmemleak areas. > So the current kfence_pool_init_late() would cause another kmemleak warning on unknown freeing. > > Reproducing test: (kfence late enable + kmemleak debug on) > > / # echo 500 > /sys/module/kfence/parameters/sample_interval > [ 153.433518] kmemleak: Freeing unknown object at 0xffff0000c0600000 > [ 153.433804] CPU: 0 PID: 100 Comm: sh Not tainted 5.19.0-rc3-74069-gde5c208d533a-dirty #1 > [ 153.434027] Hardware name: linux,dummy-virt (DT) > [ 153.434265] Call trace: > [ 153.434331] dump_backtrace+0xdc/0xfc > [ 153.434962] show_stack+0x18/0x24 > [ 153.435106] dump_stack_lvl+0x64/0x7c > [ 153.435232] dump_stack+0x18/0x38 > [ 153.435347] kmemleak_free+0x184/0x1c8 > [ 153.435462] kfence_init_pool+0x16c/0x194 > [ 153.435587] param_set_sample_interval+0xe0/0x1c4 > [ 153.435694] param_attr_store+0x98/0xf4 > [ 153.435804] module_attr_store+0x24/0x3c > [ 153.435910] sysfs_kf_write+0x3c/0x50 > ...(skip) > [ 153.444496] kfence: initialized - using 524288 bytes for 63 objects at 0x00000000a3236b01-0x00000000901655d3 > / # > > Hence, now there are two issues to solve. > (1) (The original)To prevent the undesired kmemleak scanning on the kfence pool. As Cataline's suggestion, we can just apply kmemleak_ignore_phys instead of free it at all. > ref: https://lore.kernel.org/linux-mm/YrWPg3xIHbm9bFxP@arm.com/ > > (2) The late-allocated kfence pool doesn't need to go through kmemleak_free. We can relocate the opeartion to kfence_init_pool_early() to seperate them. > That is, kfence_init_pool_early(memblock) has it and kfence_init_pool_late(page alloc) does not. > > The draft is like the following. Looks reasonable - feel free to send v2. Thanks, -- Marco