From: Joe Lawrence <[email protected]>
Module.symvers contains build-tree object paths as module identifiers
(e.g., "arch/x86/kvm/kvm") rather than runtime module names ("kvm").
Objtool's clone_reloc_klp() uses this field directly for exported
symbols, while unexported symbols correctly go through __find_modname().
This means that exported symbol relocations may land in a .klp.rela
section named with the build path rather than the module name. That is
a crash waiting to happen: the kernel's livepatch loader silently skips
this relocation because it doesn't match the expected klp_object name.
The unresolved relocation sits in the newly activated code, crashing
when executed.
Normalize export->mod at Module.symvers read time using the same logic
as __find_modname() (refactored into a shared normalize_modname()
helper).
Fixes: dd590d4d57eb ("objtool/klp: Introduce klp diff subcommand for diffing
object files")
Reported-by: Ben Procknow <[email protected]>
Signed-off-by: Joe Lawrence <[email protected]>
Reviewed-by: Miroslav Benes <[email protected]>
Signed-off-by: Josh Poimboeuf <[email protected]>
---
tools/objtool/klp-diff.c | 49 ++++++++++++++++++++++++++++------------
1 file changed, 34 insertions(+), 15 deletions(-)
diff --git a/tools/objtool/klp-diff.c b/tools/objtool/klp-diff.c
index aeb99d572300..15d37d955af0 100644
--- a/tools/objtool/klp-diff.c
+++ b/tools/objtool/klp-diff.c
@@ -83,6 +83,35 @@ static char *escape_str(const char *orig)
return new;
}
+/*
+ * Convert a build-tree object path to a runtime module name: strip
+ * directory components, replace '-' with '_', and remove file
+ * extensions. Examples:
+ *
+ * "arch/x86/kvm/kvm" -> "kvm"
+ * "arch/x86/kvm/kvm-intel" -> "kvm_intel".
+ *
+ * Used by read_exports() to normalize Module.symvers entries and by
+ * __find_modname() as a fallback when .modinfo lacks a "name=" tag.
+ */
+static char *normalize_modname(char *name)
+{
+ char *slash = strrchr(name, '/');
+
+ if (slash)
+ name = slash + 1;
+
+ for (char *c = name; *c; c++) {
+ if (*c == '-')
+ *c = '_';
+ else if (*c == '.') {
+ *c = '\0';
+ break;
+ }
+ }
+ return name;
+}
+
static int read_exports(void)
{
const char *symvers = "Module.symvers";
@@ -150,6 +179,9 @@ static int read_exports(void)
return -1;
}
+ if (strcmp(export->mod, "vmlinux"))
+ export->mod = normalize_modname(export->mod);
+
export->sym = strdup(sym);
if (!export->sym) {
ERROR_GLIBC("strdup");
@@ -1140,7 +1172,7 @@ static struct export *find_export(struct symbol *sym)
static const char *__find_modname(struct elfs *e)
{
struct section *sec;
- char *name, *slash;
+ char *name;
sec = find_section_by_name(e->orig, ".modinfo");
if (!sec) {
@@ -1158,20 +1190,7 @@ static const char *__find_modname(struct elfs *e)
return NULL;
}
- slash = strrchr(name, '/');
- if (slash)
- name = slash + 1;
-
- for (char *c = name; *c; c++) {
- if (*c == '-')
- *c = '_';
- else if (*c == '.') {
- *c = '\0';
- break;
- }
- }
-
- return name;
+ return normalize_modname(name);
}
/* Get the object's module name as defined by the kernel (and klp_object) */
--
2.54.0
