[PATCH] apparmor: fix error check

[tr...@redhat.com]

From: Tom Rix <tr...@redhat.com>

clang static analysis reports this representative problem:

label.c:1463:16: warning: Assigned value is garbage or undefined
label->hname = name;
^ ~~~~

In aa_update_label_name(), this the problem block of code

if (aa_label_acntsxprint(&name, ...) == -1)
return res;

On failure, aa_label_acntsxprint() has a more complicated return
that just -1. So check for a negative return.

It was also noted that the aa_label_acntsxprint() main comment refers
to a nonexistent parameter, so clean up the comment.

Fixes: f1bd904175e8 ("apparmor: add the base fns() for domain labels")
Signed-off-by: Tom Rix <tr...@redhat.com>
---
security/apparmor/label.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/security/apparmor/label.c b/security/apparmor/label.c
index e68bcedca976..6222fdfebe4e 100644
--- a/security/apparmor/label.c
+++ b/security/apparmor/label.c
@@ -1454,7 +1454,7 @@ bool aa_update_label_name(struct aa_ns *ns, struct aa_label *label, gfp_t gfp)
if (label->hname || labels_ns(label) != ns)
return res;

- if (aa_label_acntsxprint(&name, ns, label, FLAGS_NONE, gfp) == -1)
+ if (aa_label_acntsxprint(&name, ns, label, FLAGS_NONE, gfp) < 0)
return res;

ls = labels_set(label);
@@ -1704,7 +1704,7 @@ int aa_label_asxprint(char **strp, struct aa_ns *ns, struct aa_label *label,

/**
* aa_label_acntsxprint - allocate a __counted string buffer and print label
- * @strp: buffer to write to. (MAY BE NULL if @size == 0)
+ * @strp: buffer to write to.
* @ns: namespace profile is being viewed from
* @label: label to view (NOT NULL)
* @flags: flags controlling what label info is printed
--
2.18.1

[Nick Desaulniers]

On Sun, Oct 4, 2020 at 7:24 AM <tr...@redhat.com> wrote:
>
> From: Tom Rix <tr...@redhat.com>
>
> clang static analysis reports this representative problem:
>
> label.c:1463:16: warning: Assigned value is garbage or undefined
> label->hname = name;
> ^ ~~~~

Right, so if aa_label_acntsxprint() fails, it won't assign to its
first param. In the caller, this means assigning uninitialized memory
(UB) when aa_label_acntsxprint() returns -ENOMEM for example. Thanks
for the patch.

Reviewed-by: Nick Desaulniers <ndesau...@google.com>

> --
> You received this message because you are subscribed to the Google Groups "Clang Built Linux" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-li...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20201004142422.5717-1-trix%40redhat.com.



--
Thanks,
~Nick Desaulniers

[John Johansen]

sorry it seems I missed replying to this. This patch has been pulled into apparmor-next