CVE-2021-47126

In the Linux kernel, the following vulnerability has been resolved:

ipv6: Fix KASAN: slab-out-of-bounds Read in fib6_nh_flush_exceptions

Reported by syzbot:

HEAD commit: 90c911ad Merge tag 'fixes' of git://git.kernel.org/pub/scm..

git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master

dashboard link: https://syzkaller.appspot.com/bug?extid=123aa35098fd3c000eb7

compiler: Debian clang version 11.0.1-2

==================================================================

BUG: KASAN: slab-out-of-bounds in fib6_nh_get_excptn_bucket net/ipv6/route.c:1604 [inline]

BUG: KASAN: slab-out-of-bounds in fib6_nh_flush_exceptions+0xbd/0x360 net/ipv6/route.c:1732

Read of size 8 at addr ffff8880145c78f8 by task syz-executor.4/17760

CPU: 0 PID: 17760 Comm: syz-executor.4 Not tainted 5.12.0-rc8-syzkaller #0

Call Trace:

<IRQ>

__dump_stack lib/dump_stack.c:79 [inline]

dump_stack+0x202/0x31e lib/dump_stack.c:120

print_address_description+0x5f/0x3b0 mm/kasan/report.c:232

__kasan_report mm/kasan/report.c:399 [inline]

kasan_report+0x15c/0x200 mm/kasan/report.c:416

fib6_nh_get_excptn_bucket net/ipv6/route.c:1604 [inline]

fib6_nh_flush_exceptions+0xbd/0x360 net/ipv6/route.c:1732

fib6_nh_release+0x9a/0x430 net/ipv6/route.c:3536

fib6_info_destroy_rcu+0xcb/0x1c0 net/ipv6/ip6_fib.c:174

rcu_do_batch kernel/rcu/tree.c:2559 [inline]

rcu_core+0x8f6/0x1450 kernel/rcu/tree.c:2794

__do_softirq+0x372/0x7a6 kernel/softirq.c:345

invoke_softirq kernel/softirq.c:221 [inline]

__irq_exit_rcu+0x22c/0x260 kernel/softirq.c:422

irq_exit_rcu+0x5/0x20 kernel/softirq.c:434

sysvec_apic_timer_interrupt+0x91/0xb0 arch/x86/kernel/apic/apic.c:1100

</IRQ>

asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632

RIP: 0010:lock_acquire+0x1f6/0x720 kernel/locking/lockdep.c:5515

Code: f6 84 24 a1 00 00 00 02 0f 85 8d 02 00 00 f7 c3 00 02 00 00 49 bd 00 00 00 00 00 fc ff df 74 01 fb 48 c7 44 24 40 0e 36 e0 45 <4b> c7 44 3d 00 00 00 00 00 4b c7 44 3d 09 00 00 00 00 43 c7 44 3d

RSP: 0018:ffffc90009e06560 EFLAGS: 00000206

RAX: 1ffff920013c0cc0 RBX: 0000000000000246 RCX: dffffc0000000000

RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000

RBP: ffffc90009e066e0 R08: dffffc0000000000 R09: fffffbfff1f992b1

R10: fffffbfff1f992b1 R11: 0000000000000000 R12: 0000000000000000

R13: dffffc0000000000 R14: 0000000000000000 R15: 1ffff920013c0cb4

rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:267

rcu_read_lock include/linux/rcupdate.h:656 [inline]

ext4_get_group_info+0xea/0x340 fs/ext4/ext4.h:3231

ext4_mb_prefetch+0x123/0x5d0 fs/ext4/mballoc.c:2212

ext4_mb_regular_allocator+0x8a5/0x28f0 fs/ext4/mballoc.c:2379

ext4_mb_new_blocks+0xc6e/0x24f0 fs/ext4/mballoc.c:4982

ext4_ext_map_blocks+0x2be3/0x7210 fs/ext4/extents.c:4238

ext4_map_blocks+0xab3/0x1cb0 fs/ext4/inode.c:638

ext4_getblk+0x187/0x6c0 fs/ext4/inode.c:848

ext4_bread+0x2a/0x1c0 fs/ext4/inode.c:900

ext4_append+0x1a4/0x360 fs/ext4/namei.c:67

ext4_init_new_dir+0x337/0xa10 fs/ext4/namei.c:2768

ext4_mkdir+0x4b8/0xc00 fs/ext4/namei.c:2814

vfs_mkdir+0x45b/0x640 fs/namei.c:3819

ovl_do_mkdir fs/overlayfs/overlayfs.h:161 [inline]

ovl_mkdir_real+0x53/0x1a0 fs/overlayfs/dir.c:146

ovl_create_real+0x280/0x490 fs/overlayfs/dir.c:193

ovl_workdir_create+0x425/0x600 fs/overlayfs/super.c:788

ovl_make_workdir+0xed/0x1140 fs/overlayfs/super.c:1355

ovl_get_workdir fs/overlayfs/super.c:1492 [inline]

ovl_fill_super+0x39ee/0x5370 fs/overlayfs/super.c:2035

mount_nodev+0x52/0xe0 fs/super.c:1413

legacy_get_tree+0xea/0x180 fs/fs_context.c:592

vfs_get_tree+0x86/0x270 fs/super.c:1497

do_new_mount fs/namespace.c:2903 [inline]

path_mount+0x196f/0x2be0 fs/namespace.c:3233

do_mount fs/namespace.c:3246 [inline]

__do_sys_mount fs/namespace.c:3454 [inline]

__se_sys_mount+0x2f9/0x3b0 fs/namespace.c:3431

do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46

entry_SYSCALL_64_after_hwframe+0x44/0xae

RIP: 0033:0x4665f9

Code: ff ff c3 66 2e 0f 1f 84

---truncated---