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Summary of modules changes for the 5.13 merge window:

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- Fix an age old bug involving jump_calls and static_labels when
   CONFIG_MODULE_UNLOAD=n. When CONFIG_MODULE_UNLOAD=n, it means you
   can't unload modules, so normally the __exit sections of a module are
   not loaded at all. However, dynamic code patching (jump_label,
   static_call, alternatives) can have sites in __exit sections even if
   __exit is never executed.
 
   Reported by Peter Zijlstra: "Alternatives, jump_labels and static_call
   all can have relocations into __exit code.  Not loading it at all would
   be BAD." Therefore, load the __exit sections even when
   CONFIG_MODULE_UNLOAD=n, and discard them after init.
 
 Signed-off-by: Jessica Yu <jeyu@kernel.org>
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Merge tag 'modules-for-v5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux

Pull module updates from Jessica Yu:
 "Fix an age old bug involving jump_calls and static_labels when
  CONFIG_MODULE_UNLOAD=n.

  When CONFIG_MODULE_UNLOAD=n, it means you can't unload modules, so
  normally the __exit sections of a module are not loaded at all.
  However, dynamic code patching (jump_label, static_call, alternatives)
  can have sites in __exit sections even if __exit is never executed.

  Reported by Peter Zijlstra:
     'Alternatives, jump_labels and static_call all can have relocations
      into __exit code. Not loading it at all would be BAD.'

  Therefore, load the __exit sections even when CONFIG_MODULE_UNLOAD=n,
  and discard them after init"

* tag 'modules-for-v5.13' of git://git.kernel.org/pub/scm/linux/kernel/git/jeyu/linux:
  module: treat exit sections the same as init sections when !CONFIG_MODULE_UNLOAD
This commit is contained in:
Linus Torvalds 2021-04-30 12:29:36 -07:00
commit 65c61de9d0
1 changed files with 4 additions and 5 deletions
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9
kernel/module.c
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@ -2807,7 +2807,11 @@ void * __weak module_alloc(unsigned long size)
bool __weak module_init_section(const char *name)
{
#ifndef CONFIG_MODULE_UNLOAD
return strstarts(name, ".init") || module_exit_section(name);
#else
return strstarts(name, ".init");
#endif
}
bool __weak module_exit_section(const char *name)
@ -3121,11 +3125,6 @@ static int rewrite_section_headers(struct load_info *info, int flags)
*/
shdr->sh_addr = (size_t)info->hdr + shdr->sh_offset;
#ifndef CONFIG_MODULE_UNLOAD
/* Don't load .exit sections */
if (module_exit_section(info->secstrings+shdr->sh_name))
shdr->sh_flags &= ~(unsigned long)SHF_ALLOC;
#endif
}
/* Track but don't keep modinfo and version sections. */