Re: [PATCH] bpf: fix missing checks of the return value of check_reg_arg

[Alexei Starovoitov]

On Tue, Dec 25, 2018 at 01:17:10AM -0600, Kangjie Lu wrote:
> check_reg_arg() may fail. This fix inserts checks for its return value.
> If check_reg_arg() fails, issues an error message.
> 
> Signed-off-by: Kangjie Lu 
> ---
>  kernel/bpf/verifier.c | 15 ---
>  1 file changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 51ba84d4d34a..fde91a5c0b5a 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -2619,7 +2619,10 @@ static int check_func_call(struct bpf_verifier_env 
> *env, struct bpf_insn *insn,
>   /* after the call registers r0 - r5 were scratched */
>   for (i = 0; i < CALLER_SAVED_REGS; i++) {
>   mark_reg_not_init(env, caller->regs, caller_saved[i]);
> - check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
> + err = check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
> + if (err)
> + verbose(env,
> + "check_reg_arg() fails in setting 
> caller saved regs\n");

Such patch was already posted.
These calls cannot fail.
I prefer to leave them as-is.

[PATCH] bpf: fix missing checks of the return value of check_reg_arg

[Kangjie Lu]

check_reg_arg() may fail. This fix inserts checks for its return value.
If check_reg_arg() fails, issues an error message.

Signed-off-by: Kangjie Lu 
---
 kernel/bpf/verifier.c | 15 ---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 51ba84d4d34a..fde91a5c0b5a 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -2619,7 +2619,10 @@ static int check_func_call(struct bpf_verifier_env *env, 
struct bpf_insn *insn,
/* after the call registers r0 - r5 were scratched */
for (i = 0; i < CALLER_SAVED_REGS; i++) {
mark_reg_not_init(env, caller->regs, caller_saved[i]);
-   check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
+   err = check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
+   if (err)
+   verbose(env,
+   "check_reg_arg() fails in setting 
caller saved regs\n");
}
 
/* only increment it after check_reg_arg() finished */
@@ -2842,7 +2845,10 @@ static int check_helper_call(struct bpf_verifier_env 
*env, int func_id, int insn
/* reset caller saved regs */
for (i = 0; i < CALLER_SAVED_REGS; i++) {
mark_reg_not_init(env, regs, caller_saved[i]);
-   check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
+   err = check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
+   if (err)
+   verbose(env,
+   "check_reg_arg() fails in resetting caller 
saved regs\n");
}
 
/* update return register (already marked as written above) */
@@ -4435,7 +4441,10 @@ static int check_ld_abs(struct bpf_verifier_env *env, 
struct bpf_insn *insn)
/* reset caller saved regs to unreadable */
for (i = 0; i < CALLER_SAVED_REGS; i++) {
mark_reg_not_init(env, regs, caller_saved[i]);
-   check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
+   err = check_reg_arg(env, caller_saved[i], DST_OP_NO_MARK);
+   if (err)
+   verbose(env,
+   "check_reg_arg() fails in resetting caller 
saved regs to unreadable\n");
}
 
/* mark destination R0 register as readable, since it contains
-- 
2.17.2 (Apple Git-113)