lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Message-ID: <9d34fb0a-7aba-1e84-6426-006ea7c3d9f5@gmail.com> Date: Wed, 2 Dec 2020 20:49:06 +0200 From: Topi Miettinen <toiwoton@...il.com> To: linux-hardening@...r.kernel.org, akpm@...ux-foundation.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org Cc: Andy Lutomirski <luto@...nel.org>, Jann Horn <jannh@...gle.com>, Kees Cook <keescook@...omium.org>, Linux API <linux-api@...r.kernel.org>, Matthew Wilcox <willy@...radead.org>, Mike Rapoport <rppt@...nel.org> Subject: Re: [PATCH] mm/vmalloc: randomize vmalloc() allocations On 1.12.2020 23.45, Topi Miettinen wrote: > Memory mappings inside kernel allocated with vmalloc() are in > predictable order and packed tightly toward the low addresses. With > new kernel boot parameter 'randomize_vmalloc=1', the entire area is > used randomly to make the allocations less predictable and harder to > guess for attackers. > > Without randomize_vmalloc=1: > $ cat /proc/vmallocinfo > 0xffffc90000000000-0xffffc90000002000 8192 acpi_os_map_iomem+0x29e/0x2c0 phys=0x000000003ffe1000 ioremap > 0xffffc90000002000-0xffffc90000005000 12288 acpi_os_map_iomem+0x29e/0x2c0 phys=0x000000003ffe0000 ioremap > 0xffffc90000005000-0xffffc90000007000 8192 hpet_enable+0x36/0x4a9 phys=0x00000000fed00000 ioremap > 0xffffc90000007000-0xffffc90000009000 8192 gen_pool_add_owner+0x49/0x130 pages=1 vmalloc > 0xffffc90000009000-0xffffc9000000b000 8192 gen_pool_add_owner+0x49/0x130 pages=1 vmalloc > 0xffffc9000000b000-0xffffc9000000d000 8192 gen_pool_add_owner+0x49/0x130 pages=1 vmalloc > 0xffffc9000000d000-0xffffc9000000f000 8192 gen_pool_add_owner+0x49/0x130 pages=1 vmalloc > 0xffffc90000011000-0xffffc90000015000 16384 n_tty_open+0x16/0xe0 pages=3 vmalloc > 0xffffc900003de000-0xffffc900003e0000 8192 acpi_os_map_iomem+0x29e/0x2c0 phys=0x00000000fed00000 ioremap > 0xffffc900003e0000-0xffffc900003e2000 8192 memremap+0x1a1/0x280 phys=0x00000000000f5000 ioremap > 0xffffc900003e2000-0xffffc900003f3000 69632 pcpu_create_chunk+0x80/0x2c0 pages=16 vmalloc > 0xffffc900003f3000-0xffffc90000405000 73728 pcpu_create_chunk+0xb7/0x2c0 pages=17 vmalloc > 0xffffc90000405000-0xffffc9000040a000 20480 pcpu_create_chunk+0xed/0x2c0 pages=4 vmalloc > 0xffffe8ffffc00000-0xffffe8ffffe00000 2097152 pcpu_get_vm_areas+0x0/0x1a40 vmalloc > > With randomize_vmalloc=1, the allocations are randomized: > $ cat /proc/vmallocinfo > 0xffffca3a36442000-0xffffca3a36447000 20480 pcpu_create_chunk+0xed/0x2c0 pages=4 vmalloc > 0xffffca63034d6000-0xffffca63034d9000 12288 acpi_os_map_iomem+0x29e/0x2c0 phys=0x000000003ffe0000 ioremap > 0xffffcce23d32e000-0xffffcce23d330000 8192 memremap+0x1a1/0x280 phys=0x00000000000f5000 ioremap > 0xffffcfb9f0e22000-0xffffcfb9f0e24000 8192 hpet_enable+0x36/0x4a9 phys=0x00000000fed00000 ioremap > 0xffffd1df23e9e000-0xffffd1df23eb0000 73728 pcpu_create_chunk+0xb7/0x2c0 pages=17 vmalloc > 0xffffd690c2990000-0xffffd690c2992000 8192 acpi_os_map_iomem+0x29e/0x2c0 phys=0x000000003ffe1000 ioremap > 0xffffd8460c718000-0xffffd8460c71c000 16384 n_tty_open+0x16/0xe0 pages=3 vmalloc > 0xffffd89aba709000-0xffffd89aba70b000 8192 gen_pool_add_owner+0x49/0x130 pages=1 vmalloc > 0xffffe0ca3f2ed000-0xffffe0ca3f2ef000 8192 acpi_os_map_iomem+0x29e/0x2c0 phys=0x00000000fed00000 ioremap > 0xffffe3ba44802000-0xffffe3ba44804000 8192 gen_pool_add_owner+0x49/0x130 pages=1 vmalloc > 0xffffe4524b2a2000-0xffffe4524b2a4000 8192 gen_pool_add_owner+0x49/0x130 pages=1 vmalloc > 0xffffe61372b2e000-0xffffe61372b30000 8192 gen_pool_add_owner+0x49/0x130 pages=1 vmalloc > 0xffffe704d2f7c000-0xffffe704d2f8d000 69632 pcpu_create_chunk+0x80/0x2c0 pages=16 vmalloc > 0xffffe8ffffc00000-0xffffe8ffffe00000 2097152 pcpu_get_vm_areas+0x0/0x1a40 vmalloc > > CC: Andrew Morton <akpm@...ux-foundation.org> > CC: Andy Lutomirski <luto@...nel.org> > CC: Jann Horn <jannh@...gle.com> > CC: Kees Cook <keescook@...omium.org> > CC: Linux API <linux-api@...r.kernel.org> > CC: Matthew Wilcox <willy@...radead.org> > CC: Mike Rapoport <rppt@...nel.org> > Signed-off-by: Topi Miettinen <toiwoton@...il.com> > --- > .../admin-guide/kernel-parameters.txt | 2 ++ > mm/vmalloc.c | 25 +++++++++++++++++-- > 2 files changed, 25 insertions(+), 2 deletions(-) > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 44fde25bb221..a0242e31d2d8 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -4017,6 +4017,8 @@ > > ramdisk_start= [RAM] RAM disk image start address > > + randomize_vmalloc= [KNL] Randomize vmalloc() allocations. > + > random.trust_cpu={on,off} > [KNL] Enable or disable trusting the use of the > CPU's random number generator (if available) to > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 6ae491a8b210..a5f7bb46ddf2 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -34,6 +34,7 @@ > #include <linux/bitops.h> > #include <linux/rbtree_augmented.h> > #include <linux/overflow.h> > +#include <linux/random.h> > > #include <linux/uaccess.h> > #include <asm/tlbflush.h> > @@ -1079,6 +1080,17 @@ adjust_va_to_fit_type(struct vmap_area *va, > return 0; > } > > +static int randomize_vmalloc = 0; > + > +static int __init set_randomize_vmalloc(char *str) > +{ > + if (!str) > + return 0; > + randomize_vmalloc = simple_strtoul(str, &str, 0); > + return 1; > +} > +__setup("randomize_vmalloc=", set_randomize_vmalloc); > + > /* > * Returns a start address of the newly allocated area, if success. > * Otherwise a vend is returned that indicates failure. > @@ -1152,7 +1164,7 @@ static struct vmap_area *alloc_vmap_area(unsigned long size, > int node, gfp_t gfp_mask) > { > struct vmap_area *va, *pva; > - unsigned long addr; > + unsigned long addr, voffset; > int purged = 0; > int ret; > > @@ -1207,11 +1219,20 @@ static struct vmap_area *alloc_vmap_area(unsigned long size, > if (pva && __this_cpu_cmpxchg(ne_fit_preload_node, NULL, pva)) > kmem_cache_free(vmap_area_cachep, pva); > > + /* Randomize allocation */ > + if (randomize_vmalloc) { > + voffset = get_random_long() & (roundup_pow_of_two(vend - vstart) - 1); > + voffset = PAGE_ALIGN(voffset); > + if (voffset + size > vend - vstart) > + voffset = vend - vstart - size; > + } else > + voffset = 0; > + > /* > * If an allocation fails, the "vend" address is > * returned. Therefore trigger the overflow path. > */ > - addr = __alloc_vmap_area(size, align, vstart, vend); > + addr = __alloc_vmap_area(size, align, vstart + voffset, vend); Does not work so well after all: Dec 02 18:25:01 kernel: systemd-udevd: vmalloc: allocation failure: 10526720 bytes, mode:0xcc0(GFP_KERNEL), nodemask=(null),cpuset=/,mems_allowed=0 Dec 02 18:25:01 kernel: CPU: 12 PID: 716 Comm: systemd-udevd Tainted: G E 5.10.0-rc5+ #25 Dec 02 18:25:01 kernel: Hardware name: <redacted> Dec 02 18:25:01 kernel: Call Trace: Dec 02 18:25:01 kernel: dump_stack+0x7d/0xa3 Dec 02 18:25:01 kernel: warn_alloc.cold+0x83/0x126 Dec 02 18:25:01 kernel: ? zone_watermark_ok_safe+0x140/0x140 Dec 02 18:25:01 kernel: ? __kasan_slab_free+0x122/0x150 Dec 02 18:25:01 kernel: ? slab_free_freelist_hook+0x66/0x110 Dec 02 18:25:01 kernel: ? kfree+0xba/0x3e0 Dec 02 18:25:01 kernel: __vmalloc_node_range+0xd7/0xf0 Dec 02 18:25:01 kernel: ? load_module+0x29e0/0x3f40 Dec 02 18:25:01 kernel: module_alloc+0x9f/0x110 Dec 02 18:25:01 kernel: ? load_module+0x29e0/0x3f40 Dec 02 18:25:01 kernel: load_module+0x29e0/0x3f40 Dec 02 18:25:01 kernel: ? ima_post_read_file+0x140/0x150 Dec 02 18:25:01 kernel: ? module_frob_arch_sections+0x20/0x20 Dec 02 18:25:01 kernel: ? kernel_read_file+0x1d2/0x3e0 Dec 02 18:25:01 kernel: ? __x64_sys_fsopen+0x1f0/0x1f0 Dec 02 18:25:01 kernel: ? up_write+0x92/0x140 Dec 02 18:25:01 kernel: ? downgrade_write+0x160/0x160 Dec 02 18:25:01 kernel: ? kernel_read_file_from_fd+0x4b/0x90 Dec 02 18:25:01 kernel: __do_sys_finit_module+0x110/0x1a0 Dec 02 18:25:01 kernel: ? __x64_sys_init_module+0x50/0x50 Dec 02 18:25:01 kernel: ? get_nth_filter.part.0+0x160/0x160 Dec 02 18:25:01 kernel: ? randomize_stack_top+0x70/0x70 Dec 02 18:25:01 kernel: ? __x64_sys_fstat+0x30/0x30 Dec 02 18:25:01 kernel: ? __audit_syscall_entry+0x16a/0x1d0 Dec 02 18:25:01 kernel: ? ktime_get_coarse_real_ts64+0x4a/0x70 Dec 02 18:25:01 kernel: do_syscall_64+0x33/0x40 Dec 02 18:25:01 kernel: entry_SYSCALL_64_after_hwframe+0x44/0xa9 Dec 02 18:25:01 kernel: RIP: 0033:0xdd0fd2fb989 Dec 02 18:25:01 kernel: Code: 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d d7 54 0c 00 f7 d8 64 89 01 48 Dec 02 18:25:01 kernel: RSP: 002b:00000ceb4f03f028 EFLAGS: 00000246 ORIG_RAX: 0000000000000139 Dec 02 18:25:01 kernel: RAX: ffffffffffffffda RBX: 00000ef04a12fa90 RCX: 00000dd0fd2fb989 Dec 02 18:25:01 kernel: RDX: 0000000000000000 RSI: 000003b119220e4d RDI: 0000000000000017 Dec 02 18:25:01 kernel: RBP: 0000000000020000 R08: 0000000000000000 R09: 00000ef04a11b018 Dec 02 18:25:01 kernel: R10: 0000000000000017 R11: 0000000000000246 R12: 000003b119220e4d Dec 02 18:25:01 kernel: R13: 0000000000000000 R14: 00000ef04a124a10 R15: 00000ef04a12fa90 Dec 02 18:25:01 kernel: Mem-Info: Dec 02 18:25:01 kernel: active_anon:96 inactive_anon:17667 isolated_anon:0 active_file:15598 inactive_file:35563 isolated_file:0 unevictable:0 dirty:0 writeback:0 slab_reclaimable:8064 slab_unreclaimable:159447 mapped:10434 shmem:229 pagetables:5844 bounce:0 free:3176890 free_pcp:2892 free_cma:0 Dec 02 18:25:01 kernel: Node 0 active_anon:384kB inactive_anon:70668kB active_file:62392kB inactive_file:142252kB unevictable:0kB isolated(anon):0kB isolated(file):0kB mapped:41736kB dirty:0kB writeback:0kB shmem:916kB shmem_thp: 0kB shmem_pmdmapped: 0kB anon_thp: 0kB wri> Dec 02 18:25:01 kernel: DMA free:13860kB min:76kB low:92kB high:108kB reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:15996kB managed:15908kB mlocked:0kB pagetables:0kB bounce:0kB free_pc> Dec 02 18:25:01 kernel: lowmem_reserve[]: 0 2650 13377 13377 13377 Dec 02 18:25:01 kernel: DMA32 free:2790432kB min:13372kB low:16712kB high:20052kB reserved_highatomic:0KB active_anon:0kB inactive_anon:0kB active_file:0kB inactive_file:0kB unevictable:0kB writepending:0kB present:2796348kB managed:2796008kB mlocked:0kB pagetables:0kB bo> Dec 02 18:25:01 kernel: lowmem_reserve[]: 0 0 10726 10726 10726 Dec 02 18:25:01 kernel: Normal free:9903268kB min:54128kB low:67660kB high:81192kB reserved_highatomic:0KB active_anon:384kB inactive_anon:70668kB active_file:62392kB inactive_file:142252kB unevictable:0kB writepending:0kB present:13356288kB managed:10991672kB mlocked:0kB> Dec 02 18:25:01 kernel: lowmem_reserve[]: 0 0 0 0 0 Dec 02 18:25:01 kernel: DMA: 3*4kB (U) 1*8kB (U) 1*16kB (U) 0*32kB 2*64kB (U) 1*128kB (U) 1*256kB (U) 0*512kB 1*1024kB (U) 2*2048kB (UM) 2*4096kB (M) = 13860kB Dec 02 18:25:01 kernel: DMA32: 12*4kB (UM) 10*8kB (UM) 8*16kB (M) 9*32kB (M) 8*64kB (UM) 6*128kB (UM) 7*256kB (UM) 9*512kB (UM) 5*1024kB (UM) 6*2048kB (M) 675*4096kB (M) = 2790432kB Dec 02 18:25:01 kernel: Normal: 82*4kB (UE) 1*8kB (E) 3*16kB (UME) 16*32kB (UM) 1*64kB (U) 1*128kB (U) 1*256kB (M) 6*512kB (UM) 8*1024kB (UME) 1*2048kB (E) 2414*4096kB (M) = 9902400kB I suppose the random address happened to be too near 'vend' and no suitable block was found. Perhaps the search in __alloc_vmap_area() should then continue at 'vstart' instead (so __alloc_vmap_area() would be passed all three of vstart, voffset, vend instead of just vstart+voffset, vend). This also seems to randomize module addresses. I was going to check that next, so nice surprise! -Topi > spin_unlock(&free_vmap_area_lock); > > if (unlikely(addr == vend)) >
Powered by blists - more mailing lists