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From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: Jessica Yu <jeyu@kernel.org>
Cc: Matthias Maennich <maennich@google.com>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Joel Fernandes <joel@joelfernandes.org>,
	Martijn Coenen <maco@android.com>,
	Will Deacon <will.deacon@arm.com>,
	Masahiro Yamada <yamada.masahiro@socionext.com>,
	Michal Marek <michal.lkml@markovi.net>,
	linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH 1/7] modpost: fix broken sym->namespace for external module builds
Date: Fri, 27 Sep 2019 18:35:57 +0900
Message-ID: <20190927093603.9140-2-yamada.masahiro@socionext.com> (raw)
In-Reply-To: <20190927093603.9140-1-yamada.masahiro@socionext.com>

Currently, external module builds produce tons of false-positives:

  WARNING: module <mod> uses symbol <sym> from namespace <ns>, but does not import it.

Here, the <ns> part shows a random string.

When you build external modules, the symbol info of vmlinux and
in-kernel modules are read from $(objtree)/Module.symvers, but
read_dump() is buggy in multiple ways:

[1] When the modpost is run for vmlinux and in-kernel modules,
sym_extract_namespace() correctly allocates memory for the namespace.
On the other hand, read_dump() does not, then sym->namespace will
point to somewhere in the line buffer of get_next_line(). The data
in the buffer will be replaced soon, and sym->namespace will end up
with pointing to unrelated data. As a result, check_exports() will
show random strings in the warning messages.

[2] When there is no namespace, sym_extract_namespace() returns NULL.
On the other hand, read_dump() sets namespace to an empty string "".
(but, it will be later replaced with unrelated data due to bug [1].)
The check_exports() shows a warning unless exp->namespace is NULL,
so every symbol read from read_dump() emits the warning, which is
mostly false positive.

To address [1], I added NOFAIL(strdup(...)) to allocate memory.
For [2], I changed the if-conditional in check_exports().

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

 scripts/mod/modpost.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/scripts/mod/modpost.c b/scripts/mod/modpost.c
index 3961941e8e7a..5c628a7d80f7 100644
--- a/scripts/mod/modpost.c
+++ b/scripts/mod/modpost.c
@@ -2195,7 +2195,7 @@ static int check_exports(struct module *mod)
 		else
 			basename = mod->name;
 
-		if (exp->namespace) {
+		if (exp->namespace && exp->namespace[0]) {
 			add_namespace(&mod->required_namespaces,
 				      exp->namespace);
 
@@ -2453,7 +2453,7 @@ static void read_dump(const char *fname, unsigned int kernel)
 			mod = new_module(modname);
 			mod->skip = 1;
 		}
-		s = sym_add_exported(symname, namespace, mod,
+		s = sym_add_exported(symname, NOFAIL(strdup(namespace)), mod,
 				     export_no(export));
 		s->kernel    = kernel;
 		s->preloaded = 1;
-- 
2.17.1


  reply index

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-27  9:35 [PATCH 0/7] module: various bug-fixes and clean-ups for module namespace Masahiro Yamada
2019-09-27  9:35 ` Masahiro Yamada [this message]
2019-09-27  9:56   ` [PATCH 1/7] modpost: fix broken sym->namespace for external module builds Masahiro Yamada
2019-09-27 11:46   ` Matthias Maennich
2019-09-27  9:35 ` [PATCH 2/7] module: swap the order of symbol.namespace Masahiro Yamada
2019-09-27 12:07   ` Matthias Maennich
2019-09-27  9:35 ` [PATCH 3/7] module: rename __kstrtab_ns_* to __kstrtabns_* to avoid symbol conflict Masahiro Yamada
2019-09-27 12:14   ` Matthias Maennich
2019-09-27  9:36 ` [PATCH 4/7] module: avoid code duplication in include/linux/export.h Masahiro Yamada
2019-09-27  9:58   ` Masahiro Yamada
2019-09-27 11:07   ` Rasmus Villemoes
2019-09-27 12:36     ` Matthias Maennich
2019-10-29 19:19     ` Jessica Yu
2019-10-29 21:11       ` Rasmus Villemoes
2019-10-31 10:13         ` Jessica Yu
2019-10-31 11:03           ` Rasmus Villemoes
2019-10-31 11:26             ` Jessica Yu
2019-09-27  9:36 ` [PATCH 5/7] kbuild: fix build error of 'make nsdeps' in clean tree Masahiro Yamada
2019-09-27 12:44   ` Matthias Maennich
2019-09-27  9:36 ` [PATCH 6/7] nsdeps: fix hashbang of scripts/nsdeps Masahiro Yamada
2019-09-27 13:10   ` Matthias Maennich
2019-09-27  9:36 ` [PATCH 7/7] nsdeps: make generated patches independent of locale Masahiro Yamada
2019-09-27 13:27   ` Matthias Maennich
2019-09-27 15:42     ` Masahiro Yamada
2019-09-27 18:14       ` Greg Kroah-Hartman
2019-09-29  1:18         ` Masahiro Yamada
2019-09-29  1:30           ` Masahiro Yamada
2019-10-01 11:46             ` Matthias Maennich
2019-09-29 10:14           ` Greg Kroah-Hartman
2019-09-27 13:41 ` [PATCH 0/7] module: various bug-fixes and clean-ups for module namespace Matthias Maennich
2019-09-27 15:43   ` Masahiro Yamada
2019-10-02 18:57   ` Jessica Yu
2019-10-02 20:43     ` Matthias Maennich
2019-10-03  1:26     ` Masahiro Yamada
2019-10-03  8:03     ` Masahiro Yamada

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