svn commit: r238679 - stable/9/sys/kern

[Konstantin Belousov]

Author: kib
Date: Sun Jul 22 00:44:22 2012
New Revision: 238679
URL: http://svn.freebsd.org/changeset/base/238679

Log:
  MFC r238617:
  Fix several reads beyond the mapped first page of the binary in the
  ELF parser. Specifically, do not allow note reader and interpreter
  path comparision in the brandelf code to read past end of the page.
  This may happen if specially crafter ELF image is activated.
  
  Approved by:	re (hrs)

Modified:
  stable/9/sys/kern/imgact_elf.c
Directory Properties:
  stable/9/sys/   (props changed)

Modified: stable/9/sys/kern/imgact_elf.c
==============================================================================
--- stable/9/sys/kern/imgact_elf.c	Sat Jul 21 21:52:48 2012	(r238678)
+++ stable/9/sys/kern/imgact_elf.c	Sun Jul 22 00:44:22 2012	(r238679)
@@ -83,7 +83,7 @@ __FBSDID("$FreeBSD$");
 
 static int __elfN(check_header)(const Elf_Ehdr *hdr);
 static Elf_Brandinfo *__elfN(get_brandinfo)(struct image_params *imgp,
-    const char *interp, int32_t *osrel);
+    const char *interp, int interp_name_len, int32_t *osrel);
 static int __elfN(load_file)(struct proc *p, const char *file, u_long *addr,
     u_long *entry, size_t pagesize);
 static int __elfN(load_section)(struct vmspace *vmspace, vm_object_t object,
@@ -254,7 +254,7 @@ __elfN(brand_inuse)(Elf_Brandinfo *entry
 
 static Elf_Brandinfo *
 __elfN(get_brandinfo)(struct image_params *imgp, const char *interp,
-    int32_t *osrel)
+    int interp_name_len, int32_t *osrel)
 {
 	const Elf_Ehdr *hdr = (const Elf_Ehdr *)imgp->image_header;
 	Elf_Brandinfo *bi;
@@ -300,7 +300,10 @@ __elfN(get_brandinfo)(struct image_param
 			if (bi == NULL || bi->flags & BI_BRAND_NOTE_MANDATORY)
 				continue;
 			if (hdr->e_machine == bi->machine &&
-			    strcmp(interp, bi->interp_path) == 0)
+			    /* ELF image p_filesz includes terminating zero */
+			    strlen(bi->interp_path) + 1 == interp_name_len &&
+			    strncmp(interp, bi->interp_path, interp_name_len)
+			    == 0)
 				return (bi);
 		}
 	}
@@ -722,7 +725,7 @@ __CONCAT(exec_, __elfN(imgact))(struct i
 	u_long seg_size, seg_addr;
 	u_long addr, baddr, et_dyn_addr, entry = 0, proghdr = 0;
 	int32_t osrel = 0;
-	int error = 0, i, n;
+	int error = 0, i, n, interp_name_len = 0;
 	const char *interp = NULL, *newinterp = NULL;
 	Elf_Brandinfo *brand_info;
 	char *path;
@@ -763,9 +766,11 @@ __CONCAT(exec_, __elfN(imgact))(struct i
 		case PT_INTERP:
 			/* Path to interpreter */
 			if (phdr[i].p_filesz > MAXPATHLEN ||
-			    phdr[i].p_offset + phdr[i].p_filesz > PAGE_SIZE)
+			    phdr[i].p_offset >= PAGE_SIZE ||
+			    phdr[i].p_offset + phdr[i].p_filesz >= PAGE_SIZE)
 				return (ENOEXEC);
 			interp = imgp->image_header + phdr[i].p_offset;
+			interp_name_len = phdr[i].p_filesz;
 			break;
 		case PT_GNU_STACK:
 			if (__elfN(nxstack))
@@ -775,7 +780,8 @@ __CONCAT(exec_, __elfN(imgact))(struct i
 		}
 	}
 
-	brand_info = __elfN(get_brandinfo)(imgp, interp, &osrel);
+	brand_info = __elfN(get_brandinfo)(imgp, interp, interp_name_len,
+	    &osrel);
 	if (brand_info == NULL) {
 		uprintf("ELF binary type \"%u\" not known.\n",
 		    hdr->e_ident[EI_OSABI]);
@@ -1556,6 +1562,7 @@ __elfN(parse_notes)(struct image_params 
 	int i;
 
 	if (pnote == NULL || pnote->p_offset >= PAGE_SIZE ||
+	    pnote->p_filesz > PAGE_SIZE ||
 	    pnote->p_offset + pnote->p_filesz >= PAGE_SIZE)
 		return (FALSE);
 
@@ -1563,15 +1570,17 @@ __elfN(parse_notes)(struct image_params 
 	note_end = (const Elf_Note *)(imgp->image_header +
 	    pnote->p_offset + pnote->p_filesz);
 	for (i = 0; i < 100 && note >= note0 && note < note_end; i++) {
-		if (!aligned(note, Elf32_Addr))
+		if (!aligned(note, Elf32_Addr) || (const char *)note_end -
+		    (const char *)note < sizeof(Elf_Note))
 			return (FALSE);
 		if (note->n_namesz != checknote->hdr.n_namesz ||
 		    note->n_descsz != checknote->hdr.n_descsz ||
 		    note->n_type != checknote->hdr.n_type)
 			goto nextnote;
 		note_name = (const char *)(note + 1);
-		if (strncmp(checknote->vendor, note_name,
-		    checknote->hdr.n_namesz) != 0)
+		if (note_name + checknote->hdr.n_namesz >=
+		    (const char *)note_end || strncmp(checknote->vendor,
+		    note_name, checknote->hdr.n_namesz) != 0)
 			goto nextnote;
 
 		/*