[PATCH] binfmt_elf fix return error codes and early corrupt binary detection

With Solar Designer <solar@openwall.com>

The following patch changes the following on ELF parsing/loading code
(fs/binfmt_elf):

- Stronger validity checks on ELF files:
        treat e_phnum (program header count) < 1 as invalid
        treat p_filesz (file size) < 2 invalid on program header interp. case
 - Saner return error codes
 - Make sure SIGKILL is delivered on error handling
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

fs/binfmt_elf.c

@@ -322,7 +322,8 @@ static unsigned long load_elf_interp(struct elfhdr * interp_elf_ex,
 	 */
 	if (interp_elf_ex->e_phentsize != sizeof(struct elf_phdr))
 		goto out;
-	if (interp_elf_ex->e_phnum > 65536U / sizeof(struct elf_phdr))
+	if (interp_elf_ex->e_phnum < 1 ||
+		interp_elf_ex->e_phnum > 65536U / sizeof(struct elf_phdr))
 		goto out;
 
 	/* Now read in all of the header information */
@@ -524,12 +525,13 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
 
 	/* Now read in all of the header information */
 
-	retval = -ENOMEM;
 	if (loc->elf_ex.e_phentsize != sizeof(struct elf_phdr))
 		goto out;
-	if (loc->elf_ex.e_phnum > 65536U / sizeof(struct elf_phdr))
+	if (loc->elf_ex.e_phnum < 1 ||
+	 	loc->elf_ex.e_phnum > 65536U / sizeof(struct elf_phdr))
 		goto out;
 	size = loc->elf_ex.e_phnum * sizeof(struct elf_phdr);
+	retval = -ENOMEM;
 	elf_phdata = (struct elf_phdr *) kmalloc(size, GFP_KERNEL);
 	if (!elf_phdata)
 		goto out;
@@ -575,10 +577,12 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
 			 * is an a.out format binary
 			 */
 
-			retval = -ENOMEM;
+			retval = -ENOEXEC;
 			if (elf_ppnt->p_filesz > PATH_MAX || 
-			    elf_ppnt->p_filesz == 0)
+			    elf_ppnt->p_filesz < 2)
 				goto out_free_file;
+
+			retval = -ENOMEM;
 			elf_interpreter = (char *) kmalloc(elf_ppnt->p_filesz,
 							   GFP_KERNEL);
 			if (!elf_interpreter)
@@ -593,7 +597,7 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
 				goto out_free_interp;
 			}
 			/* make sure path is NULL terminated */
-			retval = -EINVAL;
+			retval = -ENOEXEC;
 			if (elf_interpreter[elf_ppnt->p_filesz - 1] != '\0')
 				goto out_free_interp;
 
@@ -868,8 +872,9 @@ static int load_elf_binary(struct linux_binprm * bprm, struct pt_regs * regs)
 						    interpreter,
 						    &interp_load_addr);
 		if (BAD_ADDR(elf_entry)) {
-			printk(KERN_ERR "Unable to load interpreter\n");
-			send_sig(SIGSEGV, current, 0);
+			printk(KERN_ERR "Unable to load interpreter %.128s\n",
+				elf_interpreter);
+			force_sig(SIGSEGV, current);
 			retval = -ENOEXEC; /* Nobody gets to see this, but.. */
 			goto out_free_dentry;
 		}