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BUG/MEDIUM: vars: Properly eval set-var-fmt action for emtpy log-format string

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When the log-format string was empty, in action_store() function, a fallback was
performed on the expression evaluation, thinking a set-var() was performed.
However, it is possible to have an empty log-format string. At least, on 3.2 and
3.0, it is allowed to parse an empty log-format string, quoted empty string are
not rejected.

So, on 3.2 and 3.0, it was possible to have a "set-var-fmt" action in the config
leading to parse an empty log-format string. Doing so, a crash could be
experienced when the action was executed because the fallback on the expression
evaluation led to dereference a NULL pointer.

To fix the issue, during parsing the action type is now set to a different value
for a "set-var" or a "set-var-fmt" action. And this action type is tested during
execution to perform the right action.

This patch should fix issue #3406. It must be backported as far as 3.0. Only 3.2
and 3.0 are affected by the issue.
This commit is contained in:
Christopher Faulet 2026-06-03 11:48:16 +02:00
parent 1b4255a885
commit d0ab99932a
1 changed files with 3 additions and 3 deletions
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6
src/vars.c
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@ -1030,7 +1030,7 @@ static enum act_return action_store(struct act_rule *rule, struct proxy *px,
/* Process the expression. */
memset(&smp, 0, sizeof(smp));
if (!lf_expr_isempty(&rule->arg.vars.fmt)) {
if (rule->action == 2) { /* set-var-fmt */
/* a format-string is used */
fmtstr = alloc_trash_chunk();
@ -1051,7 +1051,7 @@ static enum act_return action_store(struct act_rule *rule, struct proxy *px,
smp.data.type = SMP_T_STR;
smp.data.u.str = *fmtstr;
}
else {
else { /* set-var */
/* an expression is used */
if (!sample_process(px, sess, s, dir|SMP_OPT_FINAL,
rule->arg.vars.expr, &smp))
@ -1360,7 +1360,7 @@ static enum act_parse_ret parse_store(const char **args, int *arg, struct proxy
}
}
rule->action = ACT_CUSTOM;
rule->action = set_var;
rule->action_ptr = action_store;
rule->release_ptr = release_store_rule;
return ACT_RET_PRS_OK;