From: Kuan-Ying Lee <Kuan-Ying.Lee@xxxxxxxxxxxx> Subject: kmemleak: fix kmemleak false positive report with HW tag-based kasan enable With HW tag-based kasan enable, We will get the warning when we free object whose address starts with 0xFF. It is because kmemleak rbtree stores tagged object and this freeing object's tag does not match with rbtree object. In the example below, kmemleak rbtree stores the tagged object in the kmalloc(), and kfree() gets the pointer with 0xFF tag. Call sequence: ptr = kmalloc(size, GFP_KERNEL); page = virt_to_page(ptr); offset = offset_in_page(ptr); kfree(page_address(page) + offset); ptr = kmalloc(size, GFP_KERNEL); Call sequence like that may cause the warning as following: 1) Freeing unknown object: In kfree(), we will get free unknown object warning in kmemleak_free(). Because object(0xFx) in kmemleak rbtree and pointer(0xFF) in kfree() have different tag. 2) Overlap existing: When we allocate that object with the same hw-tag again, we will find the overlap in the kmemleak rbtree and kmemleak thread will be killed. [ 116.685312] kmemleak: Freeing unknown object at 0xffff000003f88000 [ 116.686422] CPU: 5 PID: 177 Comm: cat Not tainted 5.16.0-rc1-dirty #21 [ 116.687067] Hardware name: linux,dummy-virt (DT) [ 116.687496] Call trace: [ 116.687792] dump_backtrace+0x0/0x1ac [ 116.688255] show_stack+0x1c/0x30 [ 116.688663] dump_stack_lvl+0x68/0x84 [ 116.689096] dump_stack+0x1c/0x38 [ 116.689499] kmemleak_free+0x6c/0x70 [ 116.689919] slab_free_freelist_hook+0x104/0x200 [ 116.690420] kmem_cache_free+0xa8/0x3d4 [ 116.690845] test_version_show+0x270/0x3a0 [ 116.691344] module_attr_show+0x28/0x40 [ 116.691789] sysfs_kf_seq_show+0xb0/0x130 [ 116.692245] kernfs_seq_show+0x30/0x40 [ 116.692678] seq_read_iter+0x1bc/0x4b0 [ 116.692678] seq_read_iter+0x1bc/0x4b0 [ 116.693114] kernfs_fop_read_iter+0x144/0x1c0 [ 116.693586] generic_file_splice_read+0xd0/0x184 [ 116.694078] do_splice_to+0x90/0xe0 [ 116.694498] splice_direct_to_actor+0xb8/0x250 [ 116.694975] do_splice_direct+0x88/0xd4 [ 116.695409] do_sendfile+0x2b0/0x344 [ 116.695829] __arm64_sys_sendfile64+0x164/0x16c [ 116.696306] invoke_syscall+0x48/0x114 [ 116.696735] el0_svc_common.constprop.0+0x44/0xec [ 116.697263] do_el0_svc+0x74/0x90 [ 116.697665] el0_svc+0x20/0x80 [ 116.698261] el0t_64_sync_handler+0x1a8/0x1b0 [ 116.698695] el0t_64_sync+0x1ac/0x1b0 ... [ 117.520301] kmemleak: Cannot insert 0xf2ff000003f88000 into the object search tree (overlaps existing) [ 117.521118] CPU: 5 PID: 178 Comm: cat Not tainted 5.16.0-rc1-dirty #21 [ 117.521827] Hardware name: linux,dummy-virt (DT) [ 117.522287] Call trace: [ 117.522586] dump_backtrace+0x0/0x1ac [ 117.523053] show_stack+0x1c/0x30 [ 117.523578] dump_stack_lvl+0x68/0x84 [ 117.524039] dump_stack+0x1c/0x38 [ 117.524472] create_object.isra.0+0x2d8/0x2fc [ 117.524975] kmemleak_alloc+0x34/0x40 [ 117.525416] kmem_cache_alloc+0x23c/0x2f0 [ 117.525914] test_version_show+0x1fc/0x3a0 [ 117.526379] module_attr_show+0x28/0x40 [ 117.526827] sysfs_kf_seq_show+0xb0/0x130 [ 117.527363] kernfs_seq_show+0x30/0x40 [ 117.527848] seq_read_iter+0x1bc/0x4b0 [ 117.528320] kernfs_fop_read_iter+0x144/0x1c0 [ 117.528809] generic_file_splice_read+0xd0/0x184 [ 117.529316] do_splice_to+0x90/0xe0 [ 117.529734] splice_direct_to_actor+0xb8/0x250 [ 117.530227] do_splice_direct+0x88/0xd4 [ 117.530686] do_sendfile+0x2b0/0x344 [ 117.531154] __arm64_sys_sendfile64+0x164/0x16c [ 117.531673] invoke_syscall+0x48/0x114 [ 117.532111] el0_svc_common.constprop.0+0x44/0xec [ 117.532621] do_el0_svc+0x74/0x90 [ 117.533048] el0_svc+0x20/0x80 [ 117.533461] el0t_64_sync_handler+0x1a8/0x1b0 [ 117.533950] el0t_64_sync+0x1ac/0x1b0 [ 117.534625] kmemleak: Kernel memory leak detector disabled [ 117.535201] kmemleak: Object 0xf2ff000003f88000 (size 128): [ 117.535761] kmemleak: comm "cat", pid 177, jiffies 4294921177 [ 117.536339] kmemleak: min_count = 1 [ 117.536718] kmemleak: count = 0 [ 117.537068] kmemleak: flags = 0x1 [ 117.537429] kmemleak: checksum = 0 [ 117.537806] kmemleak: backtrace: [ 117.538211] kmem_cache_alloc+0x23c/0x2f0 [ 117.538924] test_version_show+0x1fc/0x3a0 [ 117.539393] module_attr_show+0x28/0x40 [ 117.539844] sysfs_kf_seq_show+0xb0/0x130 [ 117.540304] kernfs_seq_show+0x30/0x40 [ 117.540750] seq_read_iter+0x1bc/0x4b0 [ 117.541206] kernfs_fop_read_iter+0x144/0x1c0 [ 117.541687] generic_file_splice_read+0xd0/0x184 [ 117.542182] do_splice_to+0x90/0xe0 [ 117.542611] splice_direct_to_actor+0xb8/0x250 [ 117.543097] do_splice_direct+0x88/0xd4 [ 117.543544] do_sendfile+0x2b0/0x344 [ 117.543983] __arm64_sys_sendfile64+0x164/0x16c [ 117.544471] invoke_syscall+0x48/0x114 [ 117.544917] el0_svc_common.constprop.0+0x44/0xec [ 117.545416] do_el0_svc+0x74/0x90 [ 117.554100] kmemleak: Automatic memory scanning thread ended [akpm@xxxxxxxxxxxxxxxxxxxx: whitespace tweak] Link: https://lkml.kernel.org/r/20211118054426.4123-1-Kuan-Ying.Lee@xxxxxxxxxxxx Signed-off-by: Kuan-Ying Lee <Kuan-Ying.Lee@xxxxxxxxxxxx> Reviewed-by: Catalin Marinas <catalin.marinas@xxxxxxx> Cc: Doug Berger <opendmb@xxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/kmemleak.c | 21 ++++++++++++++------- 1 file changed, 14 insertions(+), 7 deletions(-) --- a/mm/kmemleak.c~kmemleak-fix-kmemleak-false-positive-report-with-hw-tag-based-kasan-enable +++ a/mm/kmemleak.c @@ -381,15 +381,20 @@ static void dump_object_info(struct kmem static struct kmemleak_object *lookup_object(unsigned long ptr, int alias) { struct rb_node *rb = object_tree_root.rb_node; + unsigned long untagged_ptr = (unsigned long)kasan_reset_tag((void *)ptr); while (rb) { - struct kmemleak_object *object = - rb_entry(rb, struct kmemleak_object, rb_node); - if (ptr < object->pointer) + struct kmemleak_object *object; + unsigned long untagged_objp; + + object = rb_entry(rb, struct kmemleak_object, rb_node); + untagged_objp = (unsigned long)kasan_reset_tag((void *)object->pointer); + + if (untagged_ptr < untagged_objp) rb = object->rb_node.rb_left; - else if (object->pointer + object->size <= ptr) + else if (untagged_objp + object->size <= untagged_ptr) rb = object->rb_node.rb_right; - else if (object->pointer == ptr || alias) + else if (untagged_objp == untagged_ptr || alias) return object; else { kmemleak_warn("Found object by alias at 0x%08lx\n", @@ -576,6 +581,7 @@ static struct kmemleak_object *create_ob struct kmemleak_object *object, *parent; struct rb_node **link, *rb_parent; unsigned long untagged_ptr; + unsigned long untagged_objp; object = mem_pool_alloc(gfp); if (!object) { @@ -629,9 +635,10 @@ static struct kmemleak_object *create_ob while (*link) { rb_parent = *link; parent = rb_entry(rb_parent, struct kmemleak_object, rb_node); - if (ptr + size <= parent->pointer) + untagged_objp = (unsigned long)kasan_reset_tag((void *)parent->pointer); + if (untagged_ptr + size <= untagged_objp) link = &parent->rb_node.rb_left; - else if (parent->pointer + parent->size <= ptr) + else if (untagged_objp + parent->size <= untagged_ptr) link = &parent->rb_node.rb_right; else { kmemleak_stop("Cannot insert 0x%lx into the object search tree (overlaps existing)\n", _
