| Message ID | 20220623111937.6491-2-yee.lee@mediatek.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | mm: kfence: remove kfence_pool from leak trace | expand |
On Thu, 23 Jun 2022 at 13:20, yee.lee via kasan-dev <kasan-dev@googlegroups.com> wrote: > > From: Yee Lee <yee.lee@mediatek.com> > > 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 <yee.lee@mediatek.com> > > --- > 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.
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 > <kasan-dev@googlegroups.com> wrote: > > > > From: Yee Lee <yee.lee@mediatek.com> > > > > 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 <yee.lee@mediatek.com> > > > > --- > > 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?) If so, we cannot identify later the block is stored in the phys tree(memblock) or the virt tree(page_alloc).
On Fri, 24 Jun 2022 at 10:20, 'Yee Lee' via kasan-dev <kasan-dev@googlegroups.com> 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 > > <kasan-dev@googlegroups.com> wrote: > > > > > > From: Yee Lee <yee.lee@mediatek.com> > > > > > > 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 <yee.lee@mediatek.com> > > > > > > --- > > > 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().
On Tue, 28 Jun 2022 at 08:41, Yee Lee <yee.lee@mediatek.com> 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 > <kasan-dev@googlegroups.com> 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 > <kasan-dev@googlegroups.com> wrote: > > > From: Yee Lee <yee.lee@mediatek.com> > > 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 <yee.lee@mediatek.com> > > --- > 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
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); - return 0; } @@ -831,8 +823,14 @@ void __init kfence_alloc_pool(void) { if (!kfence_sample_interval) return; - - __kfence_pool = memblock_alloc(KFENCE_POOL_SIZE, PAGE_SIZE); + /* + * The pool is live and will never be deallocated from this point on. + * Skip the pool object from the kmemleak object allocation, as it would + * otherwise overlap with allocations returned by kfence_alloc(), which + * are registered with kmemleak through the slab post-alloc hook. + */ + __kfence_pool = memblock_alloc_try_nid(KFENCE_POOL_SIZE, PAGE_SIZE, + MEMBLOCK_LOW_LIMIT, MEMBLOCK_ALLOC_NOLEAKTRACE, NUMA_NO_NODE); if (!__kfence_pool) pr_err("failed to allocate pool\n");