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From: Josh Poimboeuf <jpoimboe@redhat.com>
To: live-patching@vger.kernel.org
Cc: linux-kernel@vger.kernel.org,
	Peter Zijlstra <peterz@infradead.org>,
	Jessica Yu <jeyu@kernel.org>,
	Joe Lawrence <joe.lawrence@redhat.com>,
	Miroslav Benes <mbenes@suse.cz>
Subject: [PATCH v4 04/11] livepatch: Prevent module-specific KLP rela sections from referencing vmlinux symbols
Date: Wed, 29 Apr 2020 10:24:46 -0500	[thread overview]
Message-ID: <62e132c258390a28232f3396a3492faedb0eaa66.1588173720.git.jpoimboe@redhat.com> (raw)
In-Reply-To: <cover.1588173720.git.jpoimboe@redhat.com>

Prevent module-specific KLP rela sections from referencing vmlinux
symbols.  This helps prevent ordering issues with module special section
initializations.  Presumably such symbols are exported and normal relas
can be used instead.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Joe Lawrence <joe.lawrence@redhat.com>
Acked-by: Miroslav Benes <mbenes@suse.cz>
---
 kernel/livepatch/core.c | 38 +++++++++++++++++++++++++++-----------
 1 file changed, 27 insertions(+), 11 deletions(-)

diff --git a/kernel/livepatch/core.c b/kernel/livepatch/core.c
index 16632e75112a..f9ebb54affab 100644
--- a/kernel/livepatch/core.c
+++ b/kernel/livepatch/core.c
@@ -192,17 +192,20 @@ static int klp_find_object_symbol(const char *objname, const char *name,
 }
 
 static int klp_resolve_symbols(Elf64_Shdr *sechdrs, const char *strtab,
-			       unsigned int symndx, Elf_Shdr *relasec)
+			       unsigned int symndx, Elf_Shdr *relasec,
+			       const char *sec_objname)
 {
-	int i, cnt, vmlinux, ret;
-	char objname[MODULE_NAME_LEN];
-	char symname[KSYM_NAME_LEN];
+	int i, cnt, ret;
+	char sym_objname[MODULE_NAME_LEN];
+	char sym_name[KSYM_NAME_LEN];
 	Elf_Rela *relas;
 	Elf_Sym *sym;
 	unsigned long sympos, addr;
+	bool sym_vmlinux;
+	bool sec_vmlinux = !strcmp(sec_objname, "vmlinux");
 
 	/*
-	 * Since the field widths for objname and symname in the sscanf()
+	 * Since the field widths for sym_objname and sym_name in the sscanf()
 	 * call are hard-coded and correspond to MODULE_NAME_LEN and
 	 * KSYM_NAME_LEN respectively, we must make sure that MODULE_NAME_LEN
 	 * and KSYM_NAME_LEN have the values we expect them to have.
@@ -223,20 +226,33 @@ static int klp_resolve_symbols(Elf64_Shdr *sechdrs, const char *strtab,
 			return -EINVAL;
 		}
 
-		/* Format: .klp.sym.objname.symname,sympos */
+		/* Format: .klp.sym.sym_objname.sym_name,sympos */
 		cnt = sscanf(strtab + sym->st_name,
 			     ".klp.sym.%55[^.].%127[^,],%lu",
-			     objname, symname, &sympos);
+			     sym_objname, sym_name, &sympos);
 		if (cnt != 3) {
 			pr_err("symbol %s has an incorrectly formatted name\n",
 			       strtab + sym->st_name);
 			return -EINVAL;
 		}
 
+		sym_vmlinux = !strcmp(sym_objname, "vmlinux");
+
+		/*
+		 * Prevent module-specific KLP rela sections from referencing
+		 * vmlinux symbols.  This helps prevent ordering issues with
+		 * module special section initializations.  Presumably such
+		 * symbols are exported and normal relas can be used instead.
+		 */
+		if (!sec_vmlinux && sym_vmlinux) {
+			pr_err("invalid access to vmlinux symbol '%s' from module-specific livepatch relocation section",
+			       sym_name);
+			return -EINVAL;
+		}
+
 		/* klp_find_object_symbol() treats a NULL objname as vmlinux */
-		vmlinux = !strcmp(objname, "vmlinux");
-		ret = klp_find_object_symbol(vmlinux ? NULL : objname,
-					     symname, sympos, &addr);
+		ret = klp_find_object_symbol(sym_vmlinux ? NULL : sym_objname,
+					     sym_name, sympos, &addr);
 		if (ret)
 			return ret;
 
@@ -294,7 +310,7 @@ 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);
+	ret = klp_resolve_symbols(sechdrs, strtab, symndx, sec, sec_objname);
 	if (ret)
 		return ret;
 
-- 
2.21.1


  parent reply	other threads:[~2020-04-29 15:25 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-29 15:24 [PATCH v4 00/11] livepatch,module: Remove .klp.arch and module_disable_ro() Josh Poimboeuf
2020-04-29 15:24 ` [PATCH v4 01/11] livepatch: Disallow vmlinux.ko Josh Poimboeuf
2020-04-29 15:24 ` [PATCH v4 02/11] livepatch: Apply vmlinux-specific KLP relocations early Josh Poimboeuf
2020-04-29 15:24 ` [PATCH v4 03/11] livepatch: Remove .klp.arch Josh Poimboeuf
2020-04-29 15:24 ` Josh Poimboeuf [this message]
2020-04-29 15:24 ` [PATCH v4 05/11] s390: Change s390_kernel_write() return type to match memcpy() Josh Poimboeuf
2020-05-07 13:36   ` Jiri Kosina
2020-05-07 16:01     ` Gerald Schaefer
2020-04-29 15:24 ` [PATCH v4 06/11] s390/module: Use s390_kernel_write() for late relocations Josh Poimboeuf
2020-05-07 10:00   ` Jiri Kosina
2020-05-07 12:27     ` Gerald Schaefer
2020-04-29 15:24 ` [PATCH v4 07/11] x86/module: Use text_poke() " Josh Poimboeuf
2020-04-29 15:24 ` [PATCH v4 08/11] livepatch: Remove module_disable_ro() usage Josh Poimboeuf
2020-04-29 15:24 ` [PATCH v4 09/11] module: Remove module_disable_ro() Josh Poimboeuf
2020-04-29 15:24 ` [PATCH v4 10/11] x86/module: Use text_mutex in apply_relocate_add() Josh Poimboeuf
2020-04-29 15:24 ` [PATCH v4 11/11] module: Make module_enable_ro() static again Josh Poimboeuf
2020-04-30 11:10   ` Jessica Yu
2020-04-30 11:35     ` Miroslav Benes
2020-04-30 11:40       ` Jessica Yu
2020-04-30 12:23         ` Jessica Yu
2020-06-05 13:24   ` Guenter Roeck
2020-06-05 14:20     ` Jessica Yu
2020-06-05 14:39       ` Josh Poimboeuf
2020-04-30 11:33 ` [PATCH v4 00/11] livepatch,module: Remove .klp.arch and module_disable_ro() Jessica Yu
2020-05-04 22:20 ` Jiri Kosina
2020-05-07 22:17 ` Jiri Kosina

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