After previous commit, we are minimizing helper specific assumptions
from check_func_arg_reg_off, making it generic, and offloading checks
for a specific argument type to their respective functions called after
check_func_arg_reg_off has been called.
This allows relying on a consistent set of guarantees after that call
and then relying on them in code that deals with registers for each
argument type later. This is in line with how process_spin_lock,
process_timer_func, process_kptr_func check reg->var_off to be constant.
The same reasoning is used here to move the alignment check into
process_dynptr_func. Note that it also needs to check for constant
var_off, and accumulate the constant var_off when computing the spi in
get_spi, but that fix will come in later changes.
Acked-by: Joanne Koong <joannelkoong@xxxxxxxxx>
Signed-off-by: Kumar Kartikeya Dwivedi <memxor@xxxxxxxxx>
---
kernel/bpf/verifier.c | 13 ++++++++-----
1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index cadcf0233326..e10a21cd21a8 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -5932,6 +5932,14 @@ int process_dynptr_func(struct bpf_verifier_env *env, int regno,
verbose(env, "verifier internal error: misconfigured dynptr helper type flags\n");
return -EFAULT;
}
+ /* CONST_PTR_TO_DYNPTR already has fixed and var_off as 0 due to
+ * check_func_arg_reg_off's logic. We only need to check offset
+ * alignment for PTR_TO_STACK.
+ */
+ if (reg->type == PTR_TO_STACK && (reg->off % BPF_REG_SIZE)) {
+ verbose(env, "cannot pass in dynptr at an offset=%d\n", reg->off);
+ return -EINVAL;
+ }
/* MEM_UNINIT - Points to memory that is an appropriate candidate for
* constructing a mutable bpf_dynptr object.
*
@@ -6302,11 +6310,6 @@ int check_func_arg_reg_off(struct bpf_verifier_env *env,
switch (type) {
/* Pointer types where both fixed and variable offset is explicitly allowed: */
case PTR_TO_STACK:
- if (arg_type_is_dynptr(arg_type) && reg->off % BPF_REG_SIZE) {
- verbose(env, "cannot pass in dynptr at an offset\n");
- return -EINVAL;
- }
- fallthrough;
case PTR_TO_PACKET:
case PTR_TO_PACKET_META:
case PTR_TO_MAP_KEY:
--
2.38.1
