summaryrefslogtreecommitdiff
path: root/kernel/livepatch
diff options
context:
space:
mode:
authorSong Liu <song@kernel.org>2023-01-25 10:54:01 -0800
committerPetr Mladek <pmladek@suse.com>2023-02-03 11:28:22 +0100
commit0c05e7bd2d017a3a9a0f4e9a19ad4acf1f616f12 (patch)
tree015993873862da998d944811646938e33b76a37a /kernel/livepatch
parentbbb93362a4452282ba51067dfb609476380518dc (diff)
livepatch,x86: Clear relocation targets on a module removal
Josh reported a bug: When the object to be patched is a module, and that module is rmmod'ed and reloaded, it fails to load with: module: x86/modules: Skipping invalid relocation target, existing value is nonzero for type 2, loc 00000000ba0302e9, val ffffffffa03e293c livepatch: failed to initialize patch 'livepatch_nfsd' for module 'nfsd' (-8) livepatch: patch 'livepatch_nfsd' failed for module 'nfsd', refusing to load module 'nfsd' The livepatch module has a relocation which references a symbol in the _previous_ loading of nfsd. When apply_relocate_add() tries to replace the old relocation with a new one, it sees that the previous one is nonzero and it errors out. He also proposed three different solutions. We could remove the error check in apply_relocate_add() introduced by commit eda9cec4c9a1 ("x86/module: Detect and skip invalid relocations"). However the check is useful for detecting corrupted modules. We could also deny the patched modules to be removed. If it proved to be a major drawback for users, we could still implement a different approach. The solution would also complicate the existing code a lot. We thus decided to reverse the relocation patching (clear all relocation targets on x86_64). The solution is not universal and is too much arch-specific, but it may prove to be simpler in the end. Reported-by: Josh Poimboeuf <jpoimboe@redhat.com> Originally-by: Miroslav Benes <mbenes@suse.cz> Signed-off-by: Song Liu <song@kernel.org> Acked-by: Miroslav Benes <mbenes@suse.cz> Reviewed-by: Petr Mladek <pmladek@suse.com> Acked-by: Josh Poimboeuf <jpoimboe@kernel.org> Reviewed-by: Joe Lawrence <joe.lawrence@redhat.com> Tested-by: Joe Lawrence <joe.lawrence@redhat.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230125185401.279042-2-song@kernel.org
Diffstat (limited to 'kernel/livepatch')
-rw-r--r--kernel/livepatch/core.c62
1 files changed, 49 insertions, 13 deletions
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 9ada0bc5247b..0168c38ba187 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -261,6 +261,14 @@ static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab,
return 0;
}
+void __weak clear_relocate_add(Elf_Shdr *sechdrs,
+ const char *strtab,
+ unsigned int symindex,
+ unsigned int relsec,
+ struct module *me)
+{
+}
+
/*
* At a high-level, there are two types of klp relocation sections: those which
* reference symbols which live in vmlinux; and those which reference symbols
@@ -284,10 +292,10 @@ static int klp_resolve_symbols(Elf_Shdr *sechdrs, const char *strtab,
* the to-be-patched module to be loaded and patched sometime *after* the
* klp module is loaded.
*/
-int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
- const char *shstrtab, const char *strtab,
- unsigned int symndx, unsigned int secndx,
- const char *objname)
+static int klp_write_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
+ const char *shstrtab, const char *strtab,
+ unsigned int symndx, unsigned int secndx,
+ const char *objname, bool apply)
{
int cnt, ret;
char sec_objname[MODULE_NAME_LEN];
@@ -309,11 +317,26 @@ int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
if (strcmp(objname ? objname : "vmlinux", sec_objname))
return 0;
- ret = klp_resolve_symbols(sechdrs, strtab, symndx, sec, sec_objname);
- if (ret)
- return ret;
+ if (apply) {
+ ret = klp_resolve_symbols(sechdrs, strtab, symndx,
+ sec, sec_objname);
+ if (ret)
+ return ret;
+
+ return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
+ }
+
+ clear_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
+ return 0;
+}
- return apply_relocate_add(sechdrs, strtab, symndx, secndx, pmod);
+int klp_apply_section_relocs(struct module *pmod, Elf_Shdr *sechdrs,
+ const char *shstrtab, const char *strtab,
+ unsigned int symndx, unsigned int secndx,
+ const char *objname)
+{
+ return klp_write_section_relocs(pmod, sechdrs, shstrtab, strtab, symndx,
+ secndx, objname, true);
}
/*
@@ -762,8 +785,9 @@ static int klp_init_func(struct klp_object *obj, struct klp_func *func)
func->old_sympos ? func->old_sympos : 1);
}
-static int klp_apply_object_relocs(struct klp_patch *patch,
- struct klp_object *obj)
+static int klp_write_object_relocs(struct klp_patch *patch,
+ struct klp_object *obj,
+ bool apply)
{
int i, ret;
struct klp_modinfo *info = patch->mod->klp_info;
@@ -774,10 +798,10 @@ static int klp_apply_object_relocs(struct klp_patch *patch,
if (!(sec->sh_flags & SHF_RELA_LIVEPATCH))
continue;
- ret = klp_apply_section_relocs(patch->mod, info->sechdrs,
+ ret = klp_write_section_relocs(patch->mod, info->sechdrs,
info->secstrings,
patch->mod->core_kallsyms.strtab,
- info->symndx, i, obj->name);
+ info->symndx, i, obj->name, apply);
if (ret)
return ret;
}
@@ -785,6 +809,18 @@ static int klp_apply_object_relocs(struct klp_patch *patch,
return 0;
}
+static int klp_apply_object_relocs(struct klp_patch *patch,
+ struct klp_object *obj)
+{
+ return klp_write_object_relocs(patch, obj, true);
+}
+
+static void klp_clear_object_relocs(struct klp_patch *patch,
+ struct klp_object *obj)
+{
+ klp_write_object_relocs(patch, obj, false);
+}
+
/* parts of the initialization that is done only when the object is loaded */
static int klp_init_object_loaded(struct klp_patch *patch,
struct klp_object *obj)
@@ -1172,7 +1208,7 @@ static void klp_cleanup_module_patches_limited(struct module *mod,
klp_unpatch_object(obj);
klp_post_unpatch_callback(obj);
-
+ klp_clear_object_relocs(patch, obj);
klp_free_object_loaded(obj);
break;
}