| Message ID | 20220908230716.2751723-1-davemarchevsky@fb.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 1bfe26fb082724be453e4d7fd9bb358e3ba669b2 |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf-next] bpf: Add verifier support for custom callback return range | expand |
On 09/08, Dave Marchevsky wrote: > Verifier logic to confirm that a callback function returns 0 or 1 was > added in commit 69c087ba6225b ("bpf: Add bpf_for_each_map_elem() helper"). > At the time, callback return value was only used to continue or stop > iteration. > In order to support callbacks with a broader return value range, such as > those added in rbtree series[0] and others, add a callback_ret_range to > bpf_func_state. Verifier's helpers which set in_callback_fn will also > set the new field, which the verifier will later use to check return > value bounds. > Default to tnum_range(0, 0) instead of using tnum_unknown as a sentinel > value as the latter would prevent the valid range (0, U64_MAX) being > used. Previous global default tnum_range(0, 1) is explicitly set for > extant callback helpers. The change to global default was made after > discussion around this patch in rbtree series [1], goal here is to make > it more obvious that callback_ret_range should be explicitly set. > [0]: lore.kernel.org/bpf/20220830172759.4069786-1-davemarchevsky@fb.com/ > [1]: lore.kernel.org/bpf/20220830172759.4069786-2-davemarchevsky@fb.com/ > Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com> > --- > Sending this separately from rbtree patchset as Joanne also needs this > change for her usecase. Not sure you need that given everybody's happy about it in the separate thread, but for the sake of completion: Reviewed-by: Stanislav Fomichev <sdf@google.com>
Hello: This patch was applied to bpf/bpf-next.git (master) by Alexei Starovoitov <ast@kernel.org>: On Thu, 8 Sep 2022 16:07:16 -0700 you wrote: > Verifier logic to confirm that a callback function returns 0 or 1 was > added in commit 69c087ba6225b ("bpf: Add bpf_for_each_map_elem() helper"). > At the time, callback return value was only used to continue or stop > iteration. > > In order to support callbacks with a broader return value range, such as > those added in rbtree series[0] and others, add a callback_ret_range to > bpf_func_state. Verifier's helpers which set in_callback_fn will also > set the new field, which the verifier will later use to check return > value bounds. > > [...] Here is the summary with links: - [bpf-next] bpf: Add verifier support for custom callback return range https://git.kernel.org/bpf/bpf-next/c/1bfe26fb0827 You are awesome, thank you!
diff --git a/include/linux/bpf_verifier.h b/include/linux/bpf_verifier.h index b49a349cc6ae..e197f8fb27e2 100644 --- a/include/linux/bpf_verifier.h +++ b/include/linux/bpf_verifier.h @@ -248,6 +248,7 @@ struct bpf_func_state { */ u32 async_entry_cnt; bool in_callback_fn; + struct tnum callback_ret_range; bool in_async_callback_fn; /* The following fields should be last. See copy_func_state() */ diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index c0f175ac187a..ac0cb88e452a 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -1749,6 +1749,7 @@ static void init_func_state(struct bpf_verifier_env *env, state->callsite = callsite; state->frameno = frameno; state->subprogno = subprogno; + state->callback_ret_range = tnum_range(0, 0); init_reg_state(env, state); mark_verifier_state_scratched(env); } @@ -6789,6 +6790,7 @@ static int set_map_elem_callback_state(struct bpf_verifier_env *env, return err; callee->in_callback_fn = true; + callee->callback_ret_range = tnum_range(0, 1); return 0; } @@ -6810,6 +6812,7 @@ static int set_loop_callback_state(struct bpf_verifier_env *env, __mark_reg_not_init(env, &callee->regs[BPF_REG_5]); callee->in_callback_fn = true; + callee->callback_ret_range = tnum_range(0, 1); return 0; } @@ -6839,6 +6842,7 @@ static int set_timer_callback_state(struct bpf_verifier_env *env, __mark_reg_not_init(env, &callee->regs[BPF_REG_4]); __mark_reg_not_init(env, &callee->regs[BPF_REG_5]); callee->in_async_callback_fn = true; + callee->callback_ret_range = tnum_range(0, 1); return 0; } @@ -6866,6 +6870,7 @@ static int set_find_vma_callback_state(struct bpf_verifier_env *env, __mark_reg_not_init(env, &callee->regs[BPF_REG_4]); __mark_reg_not_init(env, &callee->regs[BPF_REG_5]); callee->in_callback_fn = true; + callee->callback_ret_range = tnum_range(0, 1); return 0; } @@ -6893,7 +6898,7 @@ static int prepare_func_exit(struct bpf_verifier_env *env, int *insn_idx) caller = state->frame[state->curframe]; if (callee->in_callback_fn) { /* enforce R0 return value range [0, 1]. */ - struct tnum range = tnum_range(0, 1); + struct tnum range = callee->callback_ret_range; if (r0->type != SCALAR_VALUE) { verbose(env, "R0 not a scalar value\n");
Verifier logic to confirm that a callback function returns 0 or 1 was added in commit 69c087ba6225b ("bpf: Add bpf_for_each_map_elem() helper"). At the time, callback return value was only used to continue or stop iteration. In order to support callbacks with a broader return value range, such as those added in rbtree series[0] and others, add a callback_ret_range to bpf_func_state. Verifier's helpers which set in_callback_fn will also set the new field, which the verifier will later use to check return value bounds. Default to tnum_range(0, 0) instead of using tnum_unknown as a sentinel value as the latter would prevent the valid range (0, U64_MAX) being used. Previous global default tnum_range(0, 1) is explicitly set for extant callback helpers. The change to global default was made after discussion around this patch in rbtree series [1], goal here is to make it more obvious that callback_ret_range should be explicitly set. [0]: lore.kernel.org/bpf/20220830172759.4069786-1-davemarchevsky@fb.com/ [1]: lore.kernel.org/bpf/20220830172759.4069786-2-davemarchevsky@fb.com/ Signed-off-by: Dave Marchevsky <davemarchevsky@fb.com> --- Sending this separately from rbtree patchset as Joanne also needs this change for her usecase. include/linux/bpf_verifier.h | 1 + kernel/bpf/verifier.c | 7 ++++++- 2 files changed, 7 insertions(+), 1 deletion(-)