[PATCH] modules: prevent overriding of symbols

eea8b54d · Ashutosh Naik <[email protected]> · 2006-01-08 01:04:25 -08:00

Ensure that an exported symbol does not already exist in the kernel or in
some other module's exported symbol table.  This is done by checking the
symbol tables for the exported symbol at the time of loading the module.
Currently this is done after the relocation of the symbol.

Signed-off-by: Ashutosh Naik <[email protected]>
Signed-off-by: Anand Krishnan <[email protected]>
Cc: Rusty Russell <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Commit: eea8b54dc0dceb740da697a89c54d20dde340306
Parents: b368fae6

Changes

1 files changed · +39 −0

File	Status	Add	Del	Content
kernel/module.c	modified	+39	−0	View file

kernel/module.c

View file

diff --git a/kernel/module.c b/kernel/module.c
index 5d9078d..fb6f091 100644
--- a/kernel/module.c
+++ b/kernel/module.c
@@ -1204,6 +1204,39 @@ void *__symbol_get(const char *symbol)
 }
 EXPORT_SYMBOL_GPL(__symbol_get);
 
+/*
+ * Ensure that an exported symbol [global namespace] does not already exist
+ * in the Kernel or in some other modules exported symbol table.
+ */
+static int verify_export_symbols(struct module *mod)
+{
+	const char *name = NULL;
+	unsigned long i, ret = 0;
+	struct module *owner;
+	const unsigned long *crc;
+
+	for (i = 0; i < mod->num_syms; i++)
+	        if (__find_symbol(mod->syms[i].name, &owner, &crc, 1)) {
+			name = mod->syms[i].name;
+			ret = -ENOEXEC;
+			goto dup;
+		}
+
+	for (i = 0; i < mod->num_gpl_syms; i++)
+	        if (__find_symbol(mod->gpl_syms[i].name, &owner, &crc, 1)) {
+			name = mod->gpl_syms[i].name;
+			ret = -ENOEXEC;
+			goto dup;
+		}
+
+dup:
+	if (ret)
+		printk(KERN_ERR "%s: exports duplicate symbol %s (owned by %s)\n",
+			mod->name, name, module_name(owner));
+
+	return ret;
+}
+
 /* Change all symbols so that sh_value encodes the pointer directly. */
 static int simplify_symbols(Elf_Shdr *sechdrs,
 			    unsigned int symindex,
@@ -1772,6 +1805,12 @@ static struct module *load_module(void __user *umod,
 			goto cleanup;
 	}
 
+        /* Find duplicate symbols */
+	err = verify_export_symbols(mod);
+
+	if (err < 0)
+		goto cleanup;
+
   	/* Set up and sort exception table */
 	mod->num_exentries = sechdrs[exindex].sh_size / sizeof(*mod->extable);
 	mod->extable = extable = (void *)sechdrs[exindex].sh_addr;