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objtool/klp: Normalize Module.symvers paths to module names

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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: dd590d4d57 ("objtool/klp: Introduce klp diff subcommand for diffing object files")
Reported-by: Ben Procknow <bprockno@redhat.com>
Signed-off-by: Joe Lawrence <joe.lawrence@redhat.com>
Signed-off-by: Josh Poimboeuf <jpoimboe@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Miroslav Benes <mbenes@suse.cz>
Cc: live-patching@vger.kernel.org
Link: https://patch.msgid.link/dbe1b72931bd3c31b751fd0729613d9f2226fff6.1785727106.git.jpoimboe@kernel.org
This commit is contained in:
Joe Lawrence
2026-08-02 20:24:24 -07:00
committed by Ingo Molnar
parent 165affd6f0
commit 8668bf91e0
1 changed files with 34 additions and 15 deletions
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49
tools/objtool/klp-diff.c
View File

@@ -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) */