modules: Skip empty sections when exporting section notes

Commit 35dead4 "modules: don't export section names of empty sections
via sysfs" changed the set of sections that have attributes, but did
not change the iteration over these attributes in add_notes_attrs().
This can lead to add_notes_attrs() creating attributes with the wrong
names or with null name pointers.

Introduce a sect_empty() function and use it in both add_sect_attrs()
and add_notes_attrs().

Reported-by: Martin Michlmayr <tbm@cyrius.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Tested-by: Martin Michlmayr <tbm@cyrius.com>
Cc: stable@kernel.org
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 10 insertions, 7 deletions

diff --git a/kernel/module.c b/kernel/module.c
index e96b8ed1cb6a..f82386bd9ee9 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1010,6 +1010,12 @@ static const struct kernel_symbol *resolve_symbol(Elf_Shdr *sechdrs,
  * J. Corbet <corbet@lwn.net>
  */
 #if defined(CONFIG_KALLSYMS) && defined(CONFIG_SYSFS)
+
+static inline bool sect_empty(const Elf_Shdr *sect)
+{
+        return !(sect->sh_flags & SHF_ALLOC) || sect->sh_size == 0;
+}
+
 struct module_sect_attr
 {
         struct module_attribute mattr;
@@ -1051,8 +1057,7 @@ static void add_sect_attrs(struct module *mod, unsigned int nsect,
 
         /* Count loaded sections and allocate structures */
         for (i = 0; i < nsect; i++)
-                if (sechdrs[i].sh_flags & SHF_ALLOC
-                    && sechdrs[i].sh_size)
+                if (!sect_empty(&sechdrs[i]))
                         nloaded++;
         size[0] = ALIGN(sizeof(*sect_attrs)
                         + nloaded * sizeof(sect_attrs->attrs[0]),
@@ -1070,9 +1075,7 @@ static void add_sect_attrs(struct module *mod, unsigned int nsect,
         sattr = &sect_attrs->attrs[0];
         gattr = &sect_attrs->grp.attrs[0];
         for (i = 0; i < nsect; i++) {
-                if (! (sechdrs[i].sh_flags & SHF_ALLOC))
-                        continue;
-                if (!sechdrs[i].sh_size)
+                if (sect_empty(&sechdrs[i]))
                         continue;
                 sattr->address = sechdrs[i].sh_addr;
                 sattr->name = kstrdup(secstrings + sechdrs[i].sh_name,
@@ -1156,7 +1159,7 @@ static void add_notes_attrs(struct module *mod, unsigned int nsect,
         /* Count notes sections and allocate structures.  */
         notes = 0;
         for (i = 0; i < nsect; i++)
-                if ((sechdrs[i].sh_flags & SHF_ALLOC) &&
+                if (!sect_empty(&sechdrs[i]) &&
                     (sechdrs[i].sh_type == SHT_NOTE))
                         ++notes;
 
@@ -1172,7 +1175,7 @@ static void add_notes_attrs(struct module *mod, unsigned int nsect,
         notes_attrs->notes = notes;
         nattr = &notes_attrs->attrs[0];
         for (loaded = i = 0; i < nsect; ++i) {
-                if (!(sechdrs[i].sh_flags & SHF_ALLOC))
+                if (sect_empty(&sechdrs[i]))
                         continue;
                 if (sechdrs[i].sh_type == SHT_NOTE) {
                         nattr->attr.name = mod->sect_attrs->attrs[loaded].name;