Commit 8ff80e96 authored by Andrey Ignatov's avatar Andrey Ignatov Committed by Alexei Starovoitov
Browse files

selftests/bpf: Test variable offset stack access 



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: default avatarAndrey Ignatov <rdna@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 2011fccf

tools/testing/selftests/bpf/verifier/var_off.c

+77 −2
Original line number Diff line number Diff line
@@ -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,

},

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