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>

diff --git a/kernel/module.c b/kernel/module.c
index e96b8ed..f82386b 100644 (file)
--- 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;