CVE-2023-52796

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

ipvlan: add ipvlan_route_v6_outbound() helper

Inspired by syzbot reports using a stack of multiple ipvlan devices.

Reduce stack size needed in ipvlan_process_v6_outbound() by moving the flowi6 struct used for the route lookup in an non inlined helper. ipvlan_route_v6_outbound() needs 120 bytes on the stack, immediately reclaimed.

Also make sure ipvlan_process_v4_outbound() is not inlined.

We might also have to lower MAX_NEST_DEV, because only syzbot uses setups with more than four stacked devices.

BUG: TASK stack guard page was hit at ffffc9000e803ff8 (stack is ffffc9000e804000..ffffc9000e808000) stack guard page: 0000 [#1] SMP KASAN CPU: 0 PID: 13442 Comm: syz-executor.4 Not tainted 6.1.52-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/09/2023 RIP: 0010:kasan_check_range+0x4/0x2a0 mm/kasan/generic.c:188 Code: 48 01 c6 48 89 c7 e8 db 4e c1 03 31 c0 5d c3 cc 0f 0b eb 02 0f 0b b8 ea ff ff ff 5d c3 cc 00 00 cc cc 00 00 cc cc 55 48 89 e5 <41> 57 41 56 41 55 41 54 53 b0 01 48 85 f6 0f 84 a4 01 00 00 48 89 RSP: 0018:ffffc9000e804000 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffffffff817e5bf2 RDX: 0000000000000000 RSI: 0000000000000008 RDI: ffffffff887c6568 RBP: ffffc9000e804000 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: dffffc0000000001 R12: 1ffff92001d0080c R13: dffffc0000000000 R14: ffffffff87e6b100 R15: 0000000000000000 FS: 00007fd0c55826c0(0000) GS:ffff8881f6800000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: ffffc9000e803ff8 CR3: 0000000170ef7000 CR4: 00000000003506f0 DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 Call Trace: <#DF> </#DF> [] __kasan_check_read+0x11/0x20 mm/kasan/shadow.c:31 [] instrument_atomic_read include/linux/instrumented.h:72 [inline] [] _test_bit include/asm-generic/bitops/instrumented-non-atomic.h:141 [inline] [] cpumask_test_cpu include/linux/cpumask.h:506 [inline] [] cpu_online include/linux/cpumask.h:1092 [inline] [] trace_lock_acquire include/trace/events/lock.h:24 [inline] [] lock_acquire+0xe2/0x590 kernel/locking/lockdep.c:5632 [] rcu_lock_acquire+0x2e/0x40 include/linux/rcupdate.h:306 [] rcu_read_lock include/linux/rcupdate.h:747 [inline] [] ip6_pol_route+0x15d/0x1440 net/ipv6/route.c:2221 [] ip6_pol_route_output+0x50/0x80 net/ipv6/route.c:2606 [] pol_lookup_func include/net/ip6_fib.h:584 [inline] [] fib6_rule_lookup+0x265/0x620 net/ipv6/fib6_rules.c:116 [] ip6_route_output_flags_noref+0x2d9/0x3a0 net/ipv6/route.c:2638 [] ip6_route_output_flags+0xca/0x340 net/ipv6/route.c:2651 [] ip6_route_output include/net/ip6_route.h:100 [inline] [] ipvlan_process_v6_outbound drivers/net/ipvlan/ipvlan_core.c:473 [inline] [] ipvlan_process_outbound drivers/net/ipvlan/ipvlan_core.c:529 [inline] [] ipvlan_xmit_mode_l3 drivers/net/ipvlan/ipvlan_core.c:602 [inline] [] ipvlan_queue_xmit+0xc33/0x1be0 drivers/net/ipvlan/ipvlan_core.c:677 [] ipvlan_start_xmit+0x49/0x100 drivers/net/ipvlan/ipvlan_main.c:229 [] netdev_start_xmit include/linux/netdevice.h:4966 [inline] [] xmit_one net/core/dev.c:3644 [inline] [] dev_hard_start_xmit+0x320/0x980 net/core/dev.c:3660 [] __dev_queue_xmit+0x16b2/0x3370 net/core/dev.c:4324 [] dev_queue_xmit include/linux/netdevice.h:3067 [inline] [] neigh_hh_output include/net/neighbour.h:529 [inline] [<f —truncated—

Weakness

The product writes data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

• For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer.

• Be wary that a language’s interface to native code may still be subject to overflows, even if the language itself is theoretically safe.

• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.

• Examples include the Safe C String Library (SafeStr) by Messier and Viega [REF-57], and the Strsafe.h library from Microsoft [REF-56]. These libraries provide safer versions of overflow-prone string-handling functions.

• Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.

• D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.

• Consider adhering to the following rules when allocating and managing an application’s memory:

• Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.

• Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.

• For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].

• Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [REF-60] [REF-61]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment.

• For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [REF-1336].

References

• https://git.kernel.org/stable/c/03cddc4df8c6be47fd27c8f8b87e5f9a989e1458
• https://git.kernel.org/stable/c/18f039428c7df183b09c69ebf10ffd4e521035d2
• https://git.kernel.org/stable/c/1f64cad3ac38ac5978b53c40e6c5e6fd3477c68f
• https://git.kernel.org/stable/c/43b781e7cb5cd0b435de276111953bf2bacd1f02
• https://git.kernel.org/stable/c/4d2d30f0792b47908af64c4d02ed1ee25ff50542
• https://git.kernel.org/stable/c/4f7f850611aa27aaaf1bf5687702ad2240ae442a
• https://git.kernel.org/stable/c/732a67ca436887b594ebc43bb5a04ffb0971a760
• https://git.kernel.org/stable/c/8872dc638c24bb774cd2224a69d72a7f661a4d56
• https://git.kernel.org/stable/c/03cddc4df8c6be47fd27c8f8b87e5f9a989e1458
• https://git.kernel.org/stable/c/18f039428c7df183b09c69ebf10ffd4e521035d2
• https://git.kernel.org/stable/c/1f64cad3ac38ac5978b53c40e6c5e6fd3477c68f
• https://git.kernel.org/stable/c/43b781e7cb5cd0b435de276111953bf2bacd1f02
• https://git.kernel.org/stable/c/4d2d30f0792b47908af64c4d02ed1ee25ff50542
• https://git.kernel.org/stable/c/4f7f850611aa27aaaf1bf5687702ad2240ae442a
• https://git.kernel.org/stable/c/732a67ca436887b594ebc43bb5a04ffb0971a760
• https://git.kernel.org/stable/c/8872dc638c24bb774cd2224a69d72a7f661a4d56