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authorKees Cook <keescook@chromium.org>2020-07-02 11:49:23 -0700
committerKees Cook <keescook@chromium.org>2020-07-08 15:59:57 -0700
commit160251842cd35a75edfb0a1d76afa3eb674ff40a (patch)
treea1ce82f3b8d23a325c151bd998b815af9574617c /kernel/kallsyms.c
parent48778464bb7d346b47157d21ffde2af6b2d39110 (diff)
kallsyms: Refactor kallsyms_show_value() to take cred
In order to perform future tests against the cred saved during open(), switch kallsyms_show_value() to operate on a cred, and have all current callers pass current_cred(). This makes it very obvious where callers are checking the wrong credential in their "read" contexts. These will be fixed in the coming patches. Additionally switch return value to bool, since it is always used as a direct permission check, not a 0-on-success, negative-on-error style function return. Cc: stable@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org>
Diffstat (limited to 'kernel/kallsyms.c')
-rw-r--r--kernel/kallsyms.c17
1 files changed, 11 insertions, 6 deletions
diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 16c8c605f4b0..bb14e64f62a4 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -644,19 +644,20 @@ static inline int kallsyms_for_perf(void)
* Otherwise, require CAP_SYSLOG (assuming kptr_restrict isn't set to
* block even that).
*/
-int kallsyms_show_value(void)
+bool kallsyms_show_value(const struct cred *cred)
{
switch (kptr_restrict) {
case 0:
if (kallsyms_for_perf())
- return 1;
+ return true;
/* fallthrough */
case 1:
- if (has_capability_noaudit(current, CAP_SYSLOG))
- return 1;
+ if (security_capable(cred, &init_user_ns, CAP_SYSLOG,
+ CAP_OPT_NOAUDIT) == 0)
+ return true;
/* fallthrough */
default:
- return 0;
+ return false;
}
}
@@ -673,7 +674,11 @@ static int kallsyms_open(struct inode *inode, struct file *file)
return -ENOMEM;
reset_iter(iter, 0);
- iter->show_value = kallsyms_show_value();
+ /*
+ * Instead of checking this on every s_show() call, cache
+ * the result here at open time.
+ */
+ iter->show_value = kallsyms_show_value(file->f_cred);
return 0;
}