[PATCH bpf v2 0/3] Fix the read of vsyscall page through bpf

[Hou Tao]

From: Hou Tao <houtao1@xxxxxxxxxx>

Hi,

As reported by syzboot [1] and [2], when trying to read vsyscall page
by using bpf_probe_read_kernel() or bpf_probe_read(), oops may happen.

Thomas Gleixner had proposed a test patch [3], but it seems that no
formal patch is posted after about one month [4], so I post it instead
and add an Originally-by tag in patch #2.

Patch #1 makes is_vsyscall_vaddr() being a common helper. Patch #2 fixes
the problem by disallowing vsyscall page read for
copy_from_kernel_nofault(). Patch #3 adds one test case to ensure the
read of vsyscall page through bpf is rejected. Please see individual
patches for more details.

Comments are always welcome.

[1]: https://lore.kernel.org/bpf/CAG48ez06TZft=ATH1qh2c5mpS5BT8UakwNkzi6nvK5_djC-4Nw@xxxxxxxxxxxxxx/
[2]: https://lore.kernel.org/bpf/CABOYnLynjBoFZOf3Z4BhaZkc5hx_kHfsjiW+UWLoB=w33LvScw@xxxxxxxxxxxxxx/
[3]: https://lore.kernel.org/bpf/87r0jwquhv.ffs@tglx/
[4]: https://lore.kernel.org/bpf/e24b125c-8ff4-9031-6c53-67ff2e01f316@xxxxxxxxxxxxxxx/

Change Log:
v2:
  * move is_vsyscall_vaddr to asm/vsyscall.h instead (Sohil)
  * elaborate on the reason for disallowing of vsyscall page read in
    copy_from_kernel_nofault_allowed() (Sohil)
  * update the commit message of patch #2 to more clearly explain how
    the oops occurs. (Sohil)
  * update the commit message of patch #3 to explain the expected return
    values of various bpf helpers (Yonghong)

v1: https://lore.kernel.org/bpf/20240119073019.1528573-1-houtao@xxxxxxxxxxxxxxx/

Hou Tao (3):
  x86/mm: Move is_vsyscall_vaddr() into asm/vsyscall.h
  x86/mm: Disallow vsyscall page read for copy_from_kernel_nofault()
  selftest/bpf: Test the read of vsyscall page under x86-64

 arch/x86/include/asm/vsyscall.h               | 10 ++++
 arch/x86/mm/fault.c                           |  9 ---
 arch/x86/mm/maccess.c                         |  9 +++
 .../selftests/bpf/prog_tests/read_vsyscall.c  | 57 +++++++++++++++++++
 .../selftests/bpf/progs/read_vsyscall.c       | 45 +++++++++++++++
 5 files changed, 121 insertions(+), 9 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/read_vsyscall.c
 create mode 100644 tools/testing/selftests/bpf/progs/read_vsyscall.c

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2.29.2