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use 48-bit address space via 4 level page tables on arm64 by default #82

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thestinger opened this issue Apr 22, 2023 · 4 comments
Open

use 48-bit address space via 4 level page tables on arm64 by default #82

thestinger opened this issue Apr 22, 2023 · 4 comments

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@thestinger
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Linux kernel defaults to 39-bit address space, providing far weaker ASLR entropy than x86_64 and also making it incompatible with hardened_malloc in the default configuration since there's not enough space. It also weakens other mitigations based on using large PROT_NONE gaps.

https://github.com/GrapheneOS/hardened_malloc

We change this in the defconfigs for Android Generic Kernel Images, but the defaults can be changed in the configuration setup instead:

GrapheneOS/kernel_common-5.15@82c2afe
GrapheneOS/kernel_common-5.15@5a4ec3d
@thestinger
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We needed to develop GrapheneOS/kernel_common-5.15@ff8f099 with a user-facing per-app toggle to work around certain apps (mostly games) being incompatible with the larger address space. I don't think that's going to be an issue anywhere else. It's almost entirely an issue with games and mostly with older versions of Unity. I think it was fixed in newer Unity. Some other games seem to have the same issue. I doubt that it's an issue for any widely used server software in practice especially since many servers are likely already using 48 bit or larger address space.

anthraxx pushed a commit that referenced this issue Jun 27, 2023
@z00467499 @gregkh
cifs: Fix warning and UAF when destroy the MR list
2d0c4f5 
[ Upstream commit 3e161c2 ]

If the MR allocate failed, the MR recovery work not initialized
and list not cleared. Then will be warning and UAF when release
the MR:

  WARNING: CPU: 4 PID: 824 at kernel/workqueue.c:3066 __flush_work.isra.0+0xf7/0x110
  CPU: 4 PID: 824 Comm: mount.cifs Not tainted 6.1.0-rc5+ #82
  RIP: 0010:__flush_work.isra.0+0xf7/0x110
  Call Trace:
   <TASK>
   __cancel_work_timer+0x2ba/0x2e0
   smbd_destroy+0x4e1/0x990
   _smbd_get_connection+0x1cbd/0x2110
   smbd_get_connection+0x21/0x40
   cifs_get_tcp_session+0x8ef/0xda0
   mount_get_conns+0x60/0x750
   cifs_mount+0x103/0xd00
   cifs_smb3_do_mount+0x1dd/0xcb0
   smb3_get_tree+0x1d5/0x300
   vfs_get_tree+0x41/0xf0
   path_mount+0x9b3/0xdd0
   __x64_sys_mount+0x190/0x1d0
   do_syscall_64+0x35/0x80
   entry_SYSCALL_64_after_hwframe+0x46/0xb0

  BUG: KASAN: use-after-free in smbd_destroy+0x4fc/0x990
  Read of size 8 at addr ffff88810b156a08 by task mount.cifs/824
  CPU: 4 PID: 824 Comm: mount.cifs Tainted: G        W          6.1.0-rc5+ #82
  Call Trace:
   dump_stack_lvl+0x34/0x44
   print_report+0x171/0x472
   kasan_report+0xad/0x130
   smbd_destroy+0x4fc/0x990
   _smbd_get_connection+0x1cbd/0x2110
   smbd_get_connection+0x21/0x40
   cifs_get_tcp_session+0x8ef/0xda0
   mount_get_conns+0x60/0x750
   cifs_mount+0x103/0xd00
   cifs_smb3_do_mount+0x1dd/0xcb0
   smb3_get_tree+0x1d5/0x300
   vfs_get_tree+0x41/0xf0
   path_mount+0x9b3/0xdd0
   __x64_sys_mount+0x190/0x1d0
   do_syscall_64+0x35/0x80
   entry_SYSCALL_64_after_hwframe+0x46/0xb0

  Allocated by task 824:
   kasan_save_stack+0x1e/0x40
   kasan_set_track+0x21/0x30
   __kasan_kmalloc+0x7a/0x90
   _smbd_get_connection+0x1b6f/0x2110
   smbd_get_connection+0x21/0x40
   cifs_get_tcp_session+0x8ef/0xda0
   mount_get_conns+0x60/0x750
   cifs_mount+0x103/0xd00
   cifs_smb3_do_mount+0x1dd/0xcb0
   smb3_get_tree+0x1d5/0x300
   vfs_get_tree+0x41/0xf0
   path_mount+0x9b3/0xdd0
   __x64_sys_mount+0x190/0x1d0
   do_syscall_64+0x35/0x80
   entry_SYSCALL_64_after_hwframe+0x46/0xb0

  Freed by task 824:
   kasan_save_stack+0x1e/0x40
   kasan_set_track+0x21/0x30
   kasan_save_free_info+0x2a/0x40
   ____kasan_slab_free+0x143/0x1b0
   __kmem_cache_free+0xc8/0x330
   _smbd_get_connection+0x1c6a/0x2110
   smbd_get_connection+0x21/0x40
   cifs_get_tcp_session+0x8ef/0xda0
   mount_get_conns+0x60/0x750
   cifs_mount+0x103/0xd00
   cifs_smb3_do_mount+0x1dd/0xcb0
   smb3_get_tree+0x1d5/0x300
   vfs_get_tree+0x41/0xf0
   path_mount+0x9b3/0xdd0
   __x64_sys_mount+0x190/0x1d0
   do_syscall_64+0x35/0x80
   entry_SYSCALL_64_after_hwframe+0x46/0xb0

Let's initialize the MR recovery work before MR allocate to prevent
the warning, remove the MRs from the list to prevent the UAF.

Fixes: c739858 ("CIFS: SMBD: Implement RDMA memory registration")
Acked-by: Paulo Alcantara (SUSE) <[email protected]>
Reviewed-by: Tom Talpey <[email protected]>
Signed-off-by: Zhang Xiaoxu <[email protected]>
Signed-off-by: Steve French <[email protected]>
Signed-off-by: Sasha Levin <[email protected]>
@sempervictus
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Is there any way to probe address space compatibility from within the kernel to conditionally set ELF_ET_DYN_BASE dependent on the userspace caller's ability handle the 48B address space? Alternatively, is it feasible to perform these checks at the alloc/libc levels to then request the correct base from ring0?

@thestinger
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No, but nearly everything does work with a 48-bit address space. The issue is that some apps have integer overflows or try to use the "unused" bits for tagging points.

@thestinger
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Very few applications still have this compatibility issue since we got Unity to fix it years ago.

anthraxx pushed a commit that referenced this issue Feb 13, 2024
@gregkh
bpf: Fix a few selftest failures due to llvm18 change
e02851a 
[ Upstream commit b16904f ]

With latest upstream llvm18, the following test cases failed:

  $ ./test_progs -j
  #13/2    bpf_cookie/multi_kprobe_link_api:FAIL
  #13/3    bpf_cookie/multi_kprobe_attach_api:FAIL
  #13      bpf_cookie:FAIL
  #77      fentry_fexit:FAIL
  #78/1    fentry_test/fentry:FAIL
  #78      fentry_test:FAIL
  #82/1    fexit_test/fexit:FAIL
  #82      fexit_test:FAIL
  #112/1   kprobe_multi_test/skel_api:FAIL
  #112/2   kprobe_multi_test/link_api_addrs:FAIL
  [...]
  #112     kprobe_multi_test:FAIL
  #356/17  test_global_funcs/global_func17:FAIL
  #356     test_global_funcs:FAIL

Further analysis shows llvm upstream patch [1] is responsible for the above
failures. For example, for function bpf_fentry_test7() in net/bpf/test_run.c,
without [1], the asm code is:

  0000000000000400 <bpf_fentry_test7>:
     400: f3 0f 1e fa                   endbr64
     404: e8 00 00 00 00                callq   0x409 <bpf_fentry_test7+0x9>
     409: 48 89 f8                      movq    %rdi, %rax
     40c: c3                            retq
     40d: 0f 1f 00                      nopl    (%rax)

... and with [1], the asm code is:

  0000000000005d20 <bpf_fentry_test7.specialized.1>:
    5d20: e8 00 00 00 00                callq   0x5d25 <bpf_fentry_test7.specialized.1+0x5>
    5d25: c3                            retq

... and <bpf_fentry_test7.specialized.1> is called instead of <bpf_fentry_test7>
and this caused test failures for #13/#77 etc. except #356.

For test case #356/17, with [1] (progs/test_global_func17.c)), the main prog
looks like:

  0000000000000000 <global_func17>:
       0:       b4 00 00 00 2a 00 00 00 w0 = 0x2a
       1:       95 00 00 00 00 00 00 00 exit

... which passed verification while the test itself expects a verification
failure.

Let us add 'barrier_var' style asm code in both places to prevent function
specialization which caused selftests failure.

  [1] llvm/llvm-project#72903

Signed-off-by: Yonghong Song <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
Signed-off-by: Sasha Levin <[email protected]>
anthraxx pushed a commit that referenced this issue Feb 13, 2024
@gregkh
bpf: Fix a few selftest failures due to llvm18 change
58bb568 
[ Upstream commit b16904f ]

With latest upstream llvm18, the following test cases failed:

  $ ./test_progs -j
  #13/2    bpf_cookie/multi_kprobe_link_api:FAIL
  #13/3    bpf_cookie/multi_kprobe_attach_api:FAIL
  #13      bpf_cookie:FAIL
  #77      fentry_fexit:FAIL
  #78/1    fentry_test/fentry:FAIL
  #78      fentry_test:FAIL
  #82/1    fexit_test/fexit:FAIL
  #82      fexit_test:FAIL
  #112/1   kprobe_multi_test/skel_api:FAIL
  #112/2   kprobe_multi_test/link_api_addrs:FAIL
  [...]
  #112     kprobe_multi_test:FAIL
  #356/17  test_global_funcs/global_func17:FAIL
  #356     test_global_funcs:FAIL

Further analysis shows llvm upstream patch [1] is responsible for the above
failures. For example, for function bpf_fentry_test7() in net/bpf/test_run.c,
without [1], the asm code is:

  0000000000000400 <bpf_fentry_test7>:
     400: f3 0f 1e fa                   endbr64
     404: e8 00 00 00 00                callq   0x409 <bpf_fentry_test7+0x9>
     409: 48 89 f8                      movq    %rdi, %rax
     40c: c3                            retq
     40d: 0f 1f 00                      nopl    (%rax)

... and with [1], the asm code is:

  0000000000005d20 <bpf_fentry_test7.specialized.1>:
    5d20: e8 00 00 00 00                callq   0x5d25 <bpf_fentry_test7.specialized.1+0x5>
    5d25: c3                            retq

... and <bpf_fentry_test7.specialized.1> is called instead of <bpf_fentry_test7>
and this caused test failures for #13/#77 etc. except #356.

For test case #356/17, with [1] (progs/test_global_func17.c)), the main prog
looks like:

  0000000000000000 <global_func17>:
       0:       b4 00 00 00 2a 00 00 00 w0 = 0x2a
       1:       95 00 00 00 00 00 00 00 exit

... which passed verification while the test itself expects a verification
failure.

Let us add 'barrier_var' style asm code in both places to prevent function
specialization which caused selftests failure.

  [1] llvm/llvm-project#72903

Signed-off-by: Yonghong Song <[email protected]>
Signed-off-by: Daniel Borkmann <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
Signed-off-by: Sasha Levin <[email protected]>
anthraxx pushed a commit that referenced this issue Jun 14, 2024
@chleroy @gregkh
powerpc/bpf/32: Fix failing test_bpf tests
0d5c132 
[ Upstream commit 8ecf3c1 ]

Recent additions in BPF like cpu v4 instructions, test_bpf module
exhibits the following failures:

  test_bpf: #82 ALU_MOVSX | BPF_B jited:1 ret 2 != 1 (0x2 != 0x1)FAIL (1 times)
  test_bpf: #83 ALU_MOVSX | BPF_H jited:1 ret 2 != 1 (0x2 != 0x1)FAIL (1 times)
  test_bpf: #84 ALU64_MOVSX | BPF_B jited:1 ret 2 != 1 (0x2 != 0x1)FAIL (1 times)
  test_bpf: #85 ALU64_MOVSX | BPF_H jited:1 ret 2 != 1 (0x2 != 0x1)FAIL (1 times)
  test_bpf: #86 ALU64_MOVSX | BPF_W jited:1 ret 2 != 1 (0x2 != 0x1)FAIL (1 times)

  test_bpf: #165 ALU_SDIV_X: -6 / 2 = -3 jited:1 ret 2147483645 != -3 (0x7ffffffd != 0xfffffffd)FAIL (1 times)
  test_bpf: #166 ALU_SDIV_K: -6 / 2 = -3 jited:1 ret 2147483645 != -3 (0x7ffffffd != 0xfffffffd)FAIL (1 times)

  test_bpf: #169 ALU_SMOD_X: -7 % 2 = -1 jited:1 ret 1 != -1 (0x1 != 0xffffffff)FAIL (1 times)
  test_bpf: #170 ALU_SMOD_K: -7 % 2 = -1 jited:1 ret 1 != -1 (0x1 != 0xffffffff)FAIL (1 times)

  test_bpf: #172 ALU64_SMOD_K: -7 % 2 = -1 jited:1 ret 1 != -1 (0x1 != 0xffffffff)FAIL (1 times)

  test_bpf: #313 BSWAP 16: 0x0123456789abcdef -> 0xefcd
  eBPF filter opcode 00d7 (@2) unsupported
  jited:0 301 PASS
  test_bpf: #314 BSWAP 32: 0x0123456789abcdef -> 0xefcdab89
  eBPF filter opcode 00d7 (@2) unsupported
  jited:0 555 PASS
  test_bpf: #315 BSWAP 64: 0x0123456789abcdef -> 0x67452301
  eBPF filter opcode 00d7 (@2) unsupported
  jited:0 268 PASS
  test_bpf: #316 BSWAP 64: 0x0123456789abcdef >> 32 -> 0xefcdab89
  eBPF filter opcode 00d7 (@2) unsupported
  jited:0 269 PASS
  test_bpf: #317 BSWAP 16: 0xfedcba9876543210 -> 0x1032
  eBPF filter opcode 00d7 (@2) unsupported
  jited:0 460 PASS
  test_bpf: #318 BSWAP 32: 0xfedcba9876543210 -> 0x10325476
  eBPF filter opcode 00d7 (@2) unsupported
  jited:0 320 PASS
  test_bpf: #319 BSWAP 64: 0xfedcba9876543210 -> 0x98badcfe
  eBPF filter opcode 00d7 (@2) unsupported
  jited:0 222 PASS
  test_bpf: #320 BSWAP 64: 0xfedcba9876543210 >> 32 -> 0x10325476
  eBPF filter opcode 00d7 (@2) unsupported
  jited:0 273 PASS

  test_bpf: #344 BPF_LDX_MEMSX | BPF_B
  eBPF filter opcode 0091 (@5) unsupported
  jited:0 432 PASS
  test_bpf: #345 BPF_LDX_MEMSX | BPF_H
  eBPF filter opcode 0089 (@5) unsupported
  jited:0 381 PASS
  test_bpf: #346 BPF_LDX_MEMSX | BPF_W
  eBPF filter opcode 0081 (@5) unsupported
  jited:0 505 PASS

  test_bpf: #490 JMP32_JA: Unconditional jump: if (true) return 1
  eBPF filter opcode 0006 (@1) unsupported
  jited:0 261 PASS

  test_bpf: Summary: 1040 PASSED, 10 FAILED, [924/1038 JIT'ed]

Fix them by adding missing processing.

Fixes: daabb2b ("bpf/tests: add tests for cpuv4 instructions")
Signed-off-by: Christophe Leroy <[email protected]>
Signed-off-by: Michael Ellerman <[email protected]>
Link: https://msgid.link/91de862dda99d170697eb79ffb478678af7e0b27.1709652689.git.christophe.leroy@csgroup.eu
Signed-off-by: Sasha Levin <[email protected]>
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@sempervictus @thestinger