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authorChris J Arges <chris.j.arges@canonical.com>2015-12-01 20:40:54 -0600
committerJiri Kosina <jkosina@suse.cz>2015-12-03 23:01:26 +0100
commitb2b018ef48675a9a524fa9791ea7d67fdac405f7 (patch)
treee683d922f21f8b88b2ae502e4d076fcaac27d898 /kernel/livepatch/core.c
parenta3d66b5a17f81ee84604f95b0e2c9ccf0434c6f0 (diff)
downloadlinux-sh-b2b018ef48675a9a524fa9791ea7d67fdac405f7.tar.gz
livepatch: add old_sympos as disambiguator field to klp_func
Currently, patching objects with duplicate symbol names fail because the creation of the sysfs function directory collides with the previous attempt. Appending old_addr to the function name is problematic as it reveals the address of the function being patch to a normal user. Using the symbol's occurrence in kallsyms to postfix the function name in the sysfs directory solves the issue of having consistent unique names and ensuring that the address is not exposed to a normal user. In addition, using the symbol position as the user's method to disambiguate symbols instead of addr allows for disambiguating symbols in modules as well for both function addresses and for relocs. This also simplifies much of the code. Special handling for kASLR is no longer needed and can be removed. The klp_find_verify_func_addr function can be replaced by klp_find_object_symbol, and klp_verify_vmlinux_symbol and its callback can be removed completely. In cases of duplicate symbols, old_sympos will be used to disambiguate instead of old_addr. By default old_sympos will be 0, and patching will only succeed if the symbol is unique. Specifying a positive value will ensure that occurrence of the symbol in kallsyms for the patched object will be used for patching if it is valid. In addition, make old_addr an internal structure field not to be specified by the user. Finally, remove klp_find_verify_func_addr as it can be replaced by klp_find_object_symbol directly. Support for symbol position disambiguation for relocations is added in the next patch in this series. Signed-off-by: Chris J Arges <chris.j.arges@canonical.com> Reviewed-by: Petr Mladek <pmladek@suse.com> Acked-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Diffstat (limited to 'kernel/livepatch/core.c')
-rw-r--r--kernel/livepatch/core.c72
1 files changed, 31 insertions, 41 deletions
diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index db545cbcdb89..e416f96e938d 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -135,13 +135,8 @@ struct klp_find_arg {
const char *objname;
const char *name;
unsigned long addr;
- /*
- * If count == 0, the symbol was not found. If count == 1, a unique
- * match was found and addr is set. If count > 1, there is
- * unresolvable ambiguity among "count" number of symbols with the same
- * name in the same object.
- */
unsigned long count;
+ unsigned long pos;
};
static int klp_find_callback(void *data, const char *name,
@@ -158,37 +153,48 @@ static int klp_find_callback(void *data, const char *name,
if (args->objname && strcmp(args->objname, mod->name))
return 0;
- /*
- * args->addr might be overwritten if another match is found
- * but klp_find_object_symbol() handles this and only returns the
- * addr if count == 1.
- */
args->addr = addr;
args->count++;
+ /*
+ * Finish the search when the symbol is found for the desired position
+ * or the position is not defined for a non-unique symbol.
+ */
+ if ((args->pos && (args->count == args->pos)) ||
+ (!args->pos && (args->count > 1)))
+ return 1;
+
return 0;
}
static int klp_find_object_symbol(const char *objname, const char *name,
- unsigned long *addr)
+ unsigned long sympos, unsigned long *addr)
{
struct klp_find_arg args = {
.objname = objname,
.name = name,
.addr = 0,
- .count = 0
+ .count = 0,
+ .pos = sympos,
};
mutex_lock(&module_mutex);
kallsyms_on_each_symbol(klp_find_callback, &args);
mutex_unlock(&module_mutex);
- if (args.count == 0)
+ /*
+ * Ensure an address was found. If sympos is 0, ensure symbol is unique;
+ * otherwise ensure the symbol position count matches sympos.
+ */
+ if (args.addr == 0)
pr_err("symbol '%s' not found in symbol table\n", name);
- else if (args.count > 1)
+ else if (args.count > 1 && sympos == 0) {
pr_err("unresolvable ambiguity (%lu matches) on symbol '%s' in object '%s'\n",
args.count, name, objname);
- else {
+ } else if (sympos != args.count && sympos > 0) {
+ pr_err("symbol position %lu for symbol '%s' in object '%s' not found\n",
+ sympos, name, objname ? objname : "vmlinux");
+ } else {
*addr = args.addr;
return 0;
}
@@ -236,27 +242,6 @@ static int klp_verify_vmlinux_symbol(const char *name, unsigned long addr)
return 0;
}
-static int klp_find_verify_func_addr(struct klp_object *obj,
- struct klp_func *func)
-{
- int ret;
-
-#if defined(CONFIG_RANDOMIZE_BASE)
- /* If KASLR has been enabled, adjust old_addr accordingly */
- if (kaslr_enabled() && func->old_addr)
- func->old_addr += kaslr_offset();
-#endif
-
- if (!func->old_addr || klp_is_module(obj))
- ret = klp_find_object_symbol(obj->name, func->old_name,
- &func->old_addr);
- else
- ret = klp_verify_vmlinux_symbol(func->old_name,
- func->old_addr);
-
- return ret;
-}
-
/*
* external symbols are located outside the parent object (where the parent
* object is either vmlinux or the kmod being patched).
@@ -276,8 +261,11 @@ static int klp_find_external_symbol(struct module *pmod, const char *name,
}
preempt_enable();
- /* otherwise check if it's in another .o within the patch module */
- return klp_find_object_symbol(pmod->name, name, addr);
+ /*
+ * Check if it's in another .o within the patch module. This also
+ * checks that the external symbol is unique.
+ */
+ return klp_find_object_symbol(pmod->name, name, 0, addr);
}
static int klp_write_object_relocations(struct module *pmod,
@@ -313,7 +301,7 @@ static int klp_write_object_relocations(struct module *pmod,
else
ret = klp_find_object_symbol(obj->mod->name,
reloc->name,
- &reloc->val);
+ 0, &reloc->val);
if (ret)
return ret;
}
@@ -756,7 +744,9 @@ static int klp_init_object_loaded(struct klp_patch *patch,
}
klp_for_each_func(obj, func) {
- ret = klp_find_verify_func_addr(obj, func);
+ ret = klp_find_object_symbol(obj->name, func->old_name,
+ func->old_sympos,
+ &func->old_addr);
if (ret)
return ret;
}