On Thu, 2025-11-20 at 15:18 +0800, Zhao Yipeng wrote: > In ima_match_rules(), if ima_filter_rule_match() returns -ENOENT due to > the rule being NULL, the function incorrectly skips the 'if (!rc)' check > and sets 'result = true'. The LSM rule is considered a match, causing > extra files to be measured by IMA. > > This issue can be reproduced in the following scenario: > After unloading the SELinux policy module via 'semodule -d', if an IMA > measurement is triggered before ima_lsm_rules is updated, > in ima_match_rules(), the first call to ima_filter_rule_match() returns > -ESTALE. This causes the code to enter the 'if (rc == -ESTALE && > !rule_reinitialized)' block, perform ima_lsm_copy_rule() and retry. In > ima_lsm_copy_rule(), since the SELinux module has been removed, the rule > becomes NULL, and the second call to ima_filter_rule_match() returns > -ENOENT. This bypasses the 'if (!rc)' check and results in a false match. > > Call trace: > selinux_audit_rule_match+0x310/0x3b8 > security_audit_rule_match+0x60/0xa0 > ima_match_rules+0x2e4/0x4a0 > ima_match_policy+0x9c/0x1e8 > ima_get_action+0x48/0x60 > process_measurement+0xf8/0xa98 > ima_bprm_check+0x98/0xd8 > security_bprm_check+0x5c/0x78 > search_binary_handler+0x6c/0x318 > exec_binprm+0x58/0x1b8 > bprm_execve+0xb8/0x130 > do_execveat_common.isra.0+0x1a8/0x258 > __arm64_sys_execve+0x48/0x68 > invoke_syscall+0x50/0x128 > el0_svc_common.constprop.0+0xc8/0xf0 > do_el0_svc+0x24/0x38 > el0_svc+0x44/0x200 > el0t_64_sync_handler+0x100/0x130 > el0t_64_sync+0x3c8/0x3d0 > > Fix this by changing 'if (!rc)' to 'if (rc <= 0)' to ensure that error > codes like -ENOENT do not bypass the check and accidentally result in a > successful match.
Thanks, it makes sense. Reviewed-by: Roberto Sassu <[email protected]> Roberto > Fixes: 4af4662fa4a9d ("integrity: IMA policy") > Signed-off-by: Zhao Yipeng <[email protected]> > --- > security/integrity/ima/ima_policy.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/security/integrity/ima/ima_policy.c > b/security/integrity/ima/ima_policy.c > index 128fab897930..db6d55af5a80 100644 > --- a/security/integrity/ima/ima_policy.c > +++ b/security/integrity/ima/ima_policy.c > @@ -674,7 +674,7 @@ static bool ima_match_rules(struct ima_rule_entry *rule, > goto retry; > } > } > - if (!rc) { > + if (rc <= 0) { > result = false; > goto out; > }
