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selftests/bpf: Test variable offset stack access

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Test different scenarios of indirect variable-offset stack access: out of
bound access (>0), min_off below initialized part of the stack,
max_off+size above initialized part of the stack, initialized stack.

Example of output:
  ...
  #856/p indirect variable-offset stack access, out of bound OK
  #857/p indirect variable-offset stack access, max_off+size > max_initialized OK
  #858/p indirect variable-offset stack access, min_off < min_initialized OK
  #859/p indirect variable-offset stack access, ok OK
  ...

Signed-off-by: Andrey Ignatov <rdna@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Andrey Ignatov 2019-03-28 18:01:58 -07:00 committed by Alexei Starovoitov
parent 2011fccfb6
commit 8ff80e96e3
1 changed files with 77 additions and 2 deletions
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79
tools/testing/selftests/bpf/verifier/var_off.c
View File

@ -40,7 +40,7 @@
.prog_type = BPF_PROG_TYPE_LWT_IN,
},
{
"indirect variable-offset stack access",
"indirect variable-offset stack access, out of bound",
.insns = {
/* Fill the top 8 bytes of the stack */
BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
@ -60,7 +60,82 @@
BPF_EXIT_INSN(),
},
.fixup_map_hash_8b = { 5 },
.errstr = "variable stack read R2",
.errstr = "invalid stack type R2 var_off",
.result = REJECT,
.prog_type = BPF_PROG_TYPE_LWT_IN,
},
{
"indirect variable-offset stack access, max_off+size > max_initialized",
.insns = {
/* Fill only the second from top 8 bytes of the stack. */
BPF_ST_MEM(BPF_DW, BPF_REG_10, -16, 0),
/* Get an unknown value. */
BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 0),
/* Make it small and 4-byte aligned. */
BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 4),
BPF_ALU64_IMM(BPF_SUB, BPF_REG_2, 16),
/* Add it to fp. We now have either fp-12 or fp-16, but we don't know
* which. fp-12 size 8 is partially uninitialized stack.
*/
BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_10),
/* Dereference it indirectly. */
BPF_LD_MAP_FD(BPF_REG_1, 0),
BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.fixup_map_hash_8b = { 5 },
.errstr = "invalid indirect read from stack var_off",
.result = REJECT,
.prog_type = BPF_PROG_TYPE_LWT_IN,
},
{
"indirect variable-offset stack access, min_off < min_initialized",
.insns = {
/* Fill only the top 8 bytes of the stack. */
BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
/* Get an unknown value */
BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 0),
/* Make it small and 4-byte aligned. */
BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 4),
BPF_ALU64_IMM(BPF_SUB, BPF_REG_2, 16),
/* Add it to fp. We now have either fp-12 or fp-16, but we don't know
* which. fp-16 size 8 is partially uninitialized stack.
*/
BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_10),
/* Dereference it indirectly. */
BPF_LD_MAP_FD(BPF_REG_1, 0),
BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.fixup_map_hash_8b = { 5 },
.errstr = "invalid indirect read from stack var_off",
.result = REJECT,
.prog_type = BPF_PROG_TYPE_LWT_IN,
},
{
"indirect variable-offset stack access, ok",
.insns = {
/* Fill the top 16 bytes of the stack. */
BPF_ST_MEM(BPF_DW, BPF_REG_10, -16, 0),
BPF_ST_MEM(BPF_DW, BPF_REG_10, -8, 0),
/* Get an unknown value. */
BPF_LDX_MEM(BPF_W, BPF_REG_2, BPF_REG_1, 0),
/* Make it small and 4-byte aligned. */
BPF_ALU64_IMM(BPF_AND, BPF_REG_2, 4),
BPF_ALU64_IMM(BPF_SUB, BPF_REG_2, 16),
/* Add it to fp. We now have either fp-12 or fp-16, we don't know
* which, but either way it points to initialized stack.
*/
BPF_ALU64_REG(BPF_ADD, BPF_REG_2, BPF_REG_10),
/* Dereference it indirectly. */
BPF_LD_MAP_FD(BPF_REG_1, 0),
BPF_EMIT_CALL(BPF_FUNC_map_lookup_elem),
BPF_MOV64_IMM(BPF_REG_0, 0),
BPF_EXIT_INSN(),
},
.fixup_map_hash_8b = { 6 },
.result = ACCEPT,
.prog_type = BPF_PROG_TYPE_LWT_IN,
},