Re: d17a1d97dc ("x86/mm/kasan: don't use vmemmap_populate() to initialize shadow"): BUG: KASAN: use-after-scope in __drm_mm_interval_first

From: Chris Wilson
Date: Mon Dec 04 2017 - 06:58:10 EST

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Quoting Dmitry Vyukov (2017-11-29 19:00:59)
> On Wed, Nov 29, 2017 at 6:21 AM, Fengguang Wu <fengguang.wu@xxxxxxxxx> wrote:
> > Greetings,
> >
> > 0day kernel testing robot got the below dmesg and the first bad commit is
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> >
> > commit d17a1d97dc208d664c91cc387ffb752c7f85dc61
> > Author: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
> > AuthorDate: Wed Nov 15 17:36:35 2017 -0800
> > Commit: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> > CommitDate: Wed Nov 15 18:21:05 2017 -0800
> >
> > x86/mm/kasan: don't use vmemmap_populate() to initialize shadow
> >
> > The kasan shadow is currently mapped using vmemmap_populate() since that
> > provides a semi-convenient way to map pages into init_top_pgt. However,
> > since that no longer zeroes the mapped pages, it is not suitable for
> > kasan, which requires zeroed shadow memory.
> >
> > Add kasan_populate_shadow() interface and use it instead of
> > vmemmap_populate(). Besides, this allows us to take advantage of
> > gigantic pages and use them to populate the shadow, which should save us
> > some memory wasted on page tables and reduce TLB pressure.
> >
> > Link: http://lkml.kernel.org/r/20171103185147.2688-2-pasha.tatashin@xxxxxxxxxx
> > Signed-off-by: Andrey Ryabinin <aryabinin@xxxxxxxxxxxxx>
> > Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
> > Cc: Steven Sistare <steven.sistare@xxxxxxxxxx>
> > Cc: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
> > Cc: Bob Picco <bob.picco@xxxxxxxxxx>
> > Cc: Michal Hocko <mhocko@xxxxxxxx>
> > Cc: Alexander Potapenko <glider@xxxxxxxxxx>
> > Cc: Ard Biesheuvel <ard.biesheuvel@xxxxxxxxxx>
> > Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
> > Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
> > Cc: David S. Miller <davem@xxxxxxxxxxxxx>
> > Cc: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
> > Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx>
> > Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
> > Cc: Ingo Molnar <mingo@xxxxxxxxxx>
> > Cc: Mark Rutland <mark.rutland@xxxxxxx>
> > Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
> > Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
> > Cc: Michal Hocko <mhocko@xxxxxxxxxx>
> > Cc: Sam Ravnborg <sam@xxxxxxxxxxxx>
> > Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> > Cc: Will Deacon <will.deacon@xxxxxxx>
> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
> >
> > a4a3ede213 mm: zero reserved and unavailable struct pages
> > d17a1d97dc x86/mm/kasan: don't use vmemmap_populate() to initialize shadow
> > 43570f0383 Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6
> > 5bef2980ad Add linux-next specific files for 20171128
> > +-------------------------------------------------------+------------+------------+------------+---------------+
> > | | a4a3ede213 | d17a1d97dc | 43570f0383 | next-20171128 |
> > +-------------------------------------------------------+------------+------------+------------+---------------+
> > | boot_successes | 30 | 0 | 0 | 0 |
> > | boot_failures | 8 | 15 | 19 | 2 |
> > | WARNING:at_drivers/pci/pci-sysfs.c:#pci_mmap_resource | 8 | | | |
> > | RIP:pci_mmap_resource | 8 | | | |
> > | BUG:KASAN:use-after-scope_in__drm_mm_interval_first | 0 | 15 | 19 | 2 |
> > +-------------------------------------------------------+------------+------------+------------+---------------+
> >
> > [ 27.628251] AMD IOMMUv2 functionality not available on this system
> > [ 27.631925] drm_mm: Testing DRM range manger (struct drm_mm), with random_seed=0x248e657d max_iterations=8192 max_prime=128
> > [ 27.633191] drm_mm: igt_sanitycheck - ok!
> > [ 79.880445] Writes: Total: 2 Max/Min: 0/0 Fail: 0
> > [ 103.749567] ==================================================================
> > [ 103.750064] BUG: KASAN: use-after-scope in __drm_mm_interval_first+0xbb/0x1bf
> > [ 103.750064] Read of size 8 at addr ffff880016577c08 by task swapper/0/1
> > [ 103.750064]
> > [ 103.750064] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 4.14.0-04319-gd17a1d9 #1
> > [ 103.750064] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
> > [ 103.750064] Call Trace:
> > [ 103.750064] ? dump_stack+0xd1/0x16c
> > [ 103.750064] ? _atomic_dec_and_lock+0x10f/0x10f
> > [ 103.750064] ? print_address_description+0x93/0x22e
> > [ 103.750064] ? __drm_mm_interval_first+0xbb/0x1bf
> > [ 103.750064] ? kasan_report+0x219/0x23f
> > [ 103.750064] ? __drm_mm_interval_first+0xbb/0x1bf
> > [ 103.750064] ? assert_continuous+0x13c/0x22f
> > [ 103.750064] ? drm_mm_replace_node+0x210/0x3ed
> > [ 103.750064] ? __igt_insert+0x5af/0xb3a
> > [ 103.750064] ? igt_bottomup+0x9e6/0x9e6
> > [ 103.750064] ? kvm_clock_read+0x21/0x29
> > [ 103.750064] ? kvm_sched_clock_read+0x5/0xd
> > [ 103.750064] ? sched_clock+0x5/0x8
> > [ 103.750064] ? sched_clock_local+0x36/0xe8
> > [ 103.750064] ? sched_clock_cpu+0x123/0x13f
> > [ 103.750064] ? rcu_irq_enter_disabled+0x8/0x8
> > [ 103.750064] ? next_prime_number+0x33f/0x368
> > [ 103.750064] ? rcu_note_context_switch+0x267/0x267
> > [ 103.750064] ? igt_replace+0x45/0xa9
> > [ 103.750064] ? test_drm_mm_init+0x112/0x164
> > [ 103.750064] ? drm_kms_helper_init+0x5/0x5
> > [ 103.750064] ? do_one_initcall+0xe7/0x1ef
> > [ 103.750064] ? initcall_blacklisted+0x15d/0x15d
> > [ 103.750064] ? up_read+0x2c/0x2c
> > [ 103.750064] ? kasan_unpoison_shadow+0xf/0x2e
> > [ 103.750064] ? kernel_init_freeable+0x2a8/0x33b
> > [ 103.750064] ? rest_init+0x24f/0x24f
> > [ 103.750064] ? kernel_init+0x7/0xfe
> > [ 103.750064] ? rest_init+0x24f/0x24f
> > [ 103.750064] ? ret_from_fork+0x24/0x30
> > [ 103.750064]
> > [ 103.750064] The buggy address belongs to the page:
> > [ 103.750064] page:ffff88001b1e3208 count:0 mapcount:0 mapping: (null) index:0x0
> > [ 103.750064] flags: 0x401fff800000()
> > [ 103.750064] raw: 0000401fff800000 0000000000000000 0000000000000000 00000000ffffffff
>
>
> Hi,
>
> I hacked a quick prototype of improvemet for KASAN for printing frame info:
>
> --- a/mm/kasan/report.c
> +++ b/mm/kasan/report.c
> @@ -289,6 +289,7 @@ static void print_shadow_for_address(const void *addr)
> int i;
> const void *shadow = kasan_mem_to_shadow(addr);
> const void *shadow_row;
> + unsigned long *ptr;
>
> shadow_row = (void *)round_down((unsigned long)shadow,
> SHADOW_BYTES_PER_ROW)
> @@ -320,6 +321,18 @@ static void print_shadow_for_address(const void *addr)
>
> shadow_row += SHADOW_BYTES_PER_ROW;
> }
> +
> +
> + ptr = (unsigned long *)((unsigned long)addr & ~7);
> + for (i = 0; i < 1000; i++, ptr--) {
> + if (*ptr == 0x41b58ab3) {
> + pr_err("\n");
> + pr_err("frame offset: %lu\n", (unsigned
> long)addr - (unsigned long)ptr);
> + pr_err("desc: '%s'\n", (const char*)*(ptr+1));
> + pr_err("func: %pS\n", (void*)*(ptr+2));
> + break;
> + }
> + }
> }
>
>
>
> And this gave me:
>
>
> [ 26.763495] ==================================================================
> [ 26.764454] BUG: KASAN: use-after-scope in __drm_mm_interval_first+0xc0/0x1e2
> [ 26.765297] Read of size 8 at addr ffff88006cb3fbe0 by task swapper/0/1
> [ 26.766081]
> [ 26.766278] CPU: 1 PID: 1 Comm: swapper/0 Not tainted
> 4.14.0-04319-gd17a1d97dc20-dirty #12
> [ 26.767760] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996),
> BIOS Bochs 01/01/2011
> [ 26.769419] Call Trace:
> [ 26.769895] dump_stack+0xdb/0x17a
> [ 26.770152] ? _atomic_dec_and_lock+0x12f/0x12f
> [ 26.770152] ? show_regs_print_info+0x5b/0x5b
> [ 26.770152] ? kasan_report+0x4d/0x247
> [ 26.770152] ? __drm_mm_interval_first+0xc0/0x1e2
> [ 26.770152] print_address_description+0x9a/0x232
> [ 26.770152] ? __drm_mm_interval_first+0xc0/0x1e2
> [ 26.770152] kasan_report+0x21e/0x247
> [ 26.770152] __asan_report_load8_noabort+0x14/0x16
> [ 26.770152] __drm_mm_interval_first+0xc0/0x1e2
> [ 26.770152] assert_continuous+0x13e/0x22f
> [ 26.770152] __igt_insert+0x665/0xc87
> [ 26.770152] ? igt_bottomup+0xaa0/0xaa0
> [ 26.770152] ? sched_clock_local+0x3c/0xfb
> [ 26.770152] ? find_held_lock+0x33/0x103
> [ 26.770152] ? next_prime_number+0x318/0x362
> [ 26.770152] ? rcu_irq_enter_disabled+0xd/0xd
> [ 26.770152] ? next_prime_number+0x337/0x362
> [ 26.770152] igt_replace+0x4b/0xb3
> [ 26.770152] test_drm_mm_init+0x118/0x172
> [ 26.770152] ? drm_kms_helper_init+0xb/0xb
> [ 26.770152] do_one_initcall+0x10f/0x21f
> [ 26.770152] ? initcall_blacklisted+0x185/0x185
> [ 26.770152] ? down_write_nested+0xa1/0x164
> [ 26.770152] ? kasan_poison_shadow+0x2f/0x31
> [ 26.770152] ? kasan_unpoison_shadow+0x14/0x35
> [ 26.770152] kernel_init_freeable+0x2ae/0x339
> [ 26.770152] ? rest_init+0x250/0x250
> [ 26.770152] kernel_init+0xc/0x105
> [ 26.770152] ? rest_init+0x250/0x250
> [ 26.770152] ret_from_fork+0x24/0x30
> [ 26.770152]
> [ 26.770152] The buggy address belongs to the page:
> [ 26.770152] page:ffff88007f39c5c8 count:0 mapcount:0 mapping:
> (null) index:0x0
> [ 26.770152] flags: 0x1a01fff800000()
> [ 26.770152] raw: 0001a01fff800000 0000000000000000 0000000000000000
> 00000000ffffffff
> [ 26.770152] raw: ffff88007f39c5e8 ffff88007f39c5e8 0000000000000000
> [ 26.770152] page dumped because: kasan: bad access detected
> [ 26.790299]
> [ 26.790299] Memory state around the buggy address:
> [ 26.790299] ffff88006cb3fa80: 00 00 00 00 00 00 00 00 00 00 00 00
> 00 00 00 f1
> [ 26.790299] ffff88006cb3fb00: f1 f1 f1 00 f2 f2 f2 f2 f2 f2 f2 00
> 00 f2 f2 f2
> [ 26.790299] >ffff88006cb3fb80: f2 f2 f2 f8 f8 f2 f2 f2 f2 f2 f2 f8
> f8 f8 f8 f8
> [ 26.790299] ^
> [ 26.790299] ffff88006cb3fc00: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
> f8 f8 f8 f2
> [ 26.790299] ffff88006cb3fc80: f2 f2 f2 00 00 00 00 00 00 00 00 00
> 00 00 00 00
> [ 26.790299]
> [ 26.790299] frame offset: 232
> [ 26.790299] desc: '5 32 8 3 __u 96 16 4 prng 160 16 7 state__ 224
> 160 3 tmp 416 224 2 mm '
> [ 26.790299] func: __igt_insert+0x0/0xc87
> [ 26.790299] ==================================================================
>
>
> That desc string is: number of local objects, then for each object:
> offset, size, name length, name.
>
> So that's variable tmp in __igt_insert.
>
> Looks very much like a real use-after-scope.

The fix should already be in mmotm:

commit 3e6e51217dd14dcda10d4bc9a38b1440e2d42c14
Author: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Date: Thu Nov 9 21:24:34 2017 +0000

lib/rbtree,drm/mm: Add rbtree_replace_node_cached()

Add a variant of rbtree_replace_node() that maintains the leftmost
cache of struct rbtree_root_cached when replacing nodes within the
rbtree.
-Chris

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