Files
linux/kernel/bpf
Ilya Leoshkevich 577c06af81 bpf: Disable zero-extension for BPF_MEMSX
On the architectures that use bpf_jit_needs_zext(), e.g., s390x, the
verifier incorrectly inserts a zero-extension after BPF_MEMSX, leading
to miscompilations like the one below:

      24:       89 1a ff fe 00 00 00 00 "r1 = *(s16 *)(r10 - 2);"       # zext_dst set
   0x3ff7fdb910e:       lgh     %r2,-2(%r13,%r0)                        # load halfword
   0x3ff7fdb9114:       llgfr   %r2,%r2                                 # wrong!
      25:       65 10 00 03 00 00 7f ff if r1 s> 32767 goto +3 <l0_1>   # check_cond_jmp_op()

Disable such zero-extensions. The JITs need to insert sign-extension
themselves, if necessary.

Suggested-by: Puranjay Mohan <puranjay12@gmail.com>
Signed-off-by: Ilya Leoshkevich <iii@linux.ibm.com>
Reviewed-by: Puranjay Mohan <puranjay12@gmail.com>
Link: https://lore.kernel.org/r/20230919101336.2223655-2-iii@linux.ibm.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
2023-09-21 14:21:59 -07:00
..
2023-03-08 16:19:51 -08:00
2022-05-10 11:20:45 -07:00
2020-08-28 15:41:30 +02:00
2023-07-31 14:44:02 -07:00