forked from Minki/linux
f4483f2cc1
When a tail call fails, it is documented that the tail call should
continue execution at the following instruction. An example tail call
sequence is:
12: (85) call bpf_tail_call#12
13: (b7) r0 = 0
14: (95) exit
The ARM assembler for the tail call in this case ends up branching to
instruction 14 instead of instruction 13, resulting in the BPF filter
returning a non-zero value:
178: ldr r8, [sp, #588] ; insn 12
17c: ldr r6, [r8, r6]
180: ldr r8, [sp, #580]
184: cmp r8, r6
188: bcs 0x1e8
18c: ldr r6, [sp, #524]
190: ldr r7, [sp, #528]
194: cmp r7, #0
198: cmpeq r6, #32
19c: bhi 0x1e8
1a0: adds r6, r6, #1
1a4: adc r7, r7, #0
1a8: str r6, [sp, #524]
1ac: str r7, [sp, #528]
1b0: mov r6, #104
1b4: ldr r8, [sp, #588]
1b8: add r6, r8, r6
1bc: ldr r8, [sp, #580]
1c0: lsl r7, r8, #2
1c4: ldr r6, [r6, r7]
1c8: cmp r6, #0
1cc: beq 0x1e8
1d0: mov r8, #32
1d4: ldr r6, [r6, r8]
1d8: add r6, r6, #44
1dc: bx r6
1e0: mov r0, #0 ; insn 13
1e4: mov r1, #0
1e8: add sp, sp, #596 ; insn 14
1ec: pop {r4, r5, r6, r7, r8, sl, pc}
For other sequences, the tail call could end up branching midway through
the following BPF instructions, or maybe off the end of the function,
leading to unknown behaviours.
Fixes:
|
||
|---|---|---|
| .. | ||
| alpha | ||
| arc | ||
| arm | ||
| arm64 | ||
| blackfin | ||
| c6x | ||
| cris | ||
| frv | ||
| h8300 | ||
| hexagon | ||
| ia64 | ||
| m32r | ||
| m68k | ||
| metag | ||
| microblaze | ||
| mips | ||
| mn10300 | ||
| nios2 | ||
| openrisc | ||
| parisc | ||
| powerpc | ||
| riscv | ||
| s390 | ||
| score | ||
| sh | ||
| sparc | ||
| tile | ||
| um | ||
| unicore32 | ||
| x86 | ||
| xtensa | ||
| .gitignore | ||
| Kconfig | ||