[src/trunk]: src/sys/kern When reading from /dev/ksyms we need to skip over e...

[pgoyette <pgoyette%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/76753d92c791
branches:  trunk
changeset: 968187:76753d92c791
user:      pgoyette <pgoyette%NetBSD.org@localhost>
date:      Sun Jan 05 21:12:34 2020 +0000

description:
When reading from /dev/ksyms we need to skip over entries that have
been marked as sd_gone.  Otherwise we might try to uiomove() data from
memory that has been unmapped, resulting in EFAULT.

XXX This (along with other pre-existing checks st->sd_gone) is still
racy, but it's an improvement over current code.  Ideally we would
make a complete copy of the symbol table when we open /dev/ksyms so
we could ignore any changes that occur.

ad@ says "good enough for now"

XXX Pullup to -9 and -8

diffstat:

 sys/kern/kern_ksyms.c |  12 +++++++++---
 1 files changed, 9 insertions(+), 3 deletions(-)

diffs (56 lines):

diff -r 3858235668a4 -r 76753d92c791 sys/kern/kern_ksyms.c
--- a/sys/kern/kern_ksyms.c     Sun Jan 05 20:52:15 2020 +0000
+++ b/sys/kern/kern_ksyms.c     Sun Jan 05 21:12:34 2020 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: kern_ksyms.c,v 1.87 2017/11/04 22:17:55 christos Exp $ */
+/*     $NetBSD: kern_ksyms.c,v 1.88 2020/01/05 21:12:34 pgoyette Exp $ */
 
 /*-
  * Copyright (c) 2008 The NetBSD Foundation, Inc.
@@ -73,7 +73,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_ksyms.c,v 1.87 2017/11/04 22:17:55 christos Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_ksyms.c,v 1.88 2020/01/05 21:12:34 pgoyette Exp $");
 
 #if defined(_KERNEL) && defined(_KERNEL_OPT)
 #include "opt_copy_symtab.h"
@@ -765,9 +765,9 @@
                if (strcmp(name, st->sd_name) != 0)
                        continue;
                st->sd_gone = true;
+               ksyms_sizes_calc();
                if (!ksyms_isopen) {
                        TAILQ_REMOVE(&ksyms_symtabs, st, sd_queue);
-                       ksyms_sizes_calc();
                        kmem_free(st->sd_nmap,
                                  st->sd_nmapsize * sizeof(uint32_t));
                        kmem_free(st, sizeof(*st));
@@ -856,6 +856,8 @@
 
        ksyms_symsz = ksyms_strsz = 0;
        TAILQ_FOREACH(st, &ksyms_symtabs, sd_queue) {
+               if (__predict_false(st->sd_gone))
+                       continue;
                delta = ksyms_strsz - st->sd_usroffset;
                if (delta != 0) {
                        for (i = 0; i < st->sd_symsize/sizeof(Elf_Sym); i++)
@@ -1034,6 +1036,8 @@
         */
        filepos = sizeof(struct ksyms_hdr);
        TAILQ_FOREACH(st, &ksyms_symtabs, sd_queue) {
+               if (__predict_false(st->sd_gone))
+                       continue;
                if (uio->uio_resid == 0)
                        return 0;
                if (uio->uio_offset <= st->sd_symsize + filepos) {
@@ -1052,6 +1056,8 @@
        KASSERT(filepos == sizeof(struct ksyms_hdr) +
            ksyms_hdr.kh_shdr[SYMTAB].sh_size);
        TAILQ_FOREACH(st, &ksyms_symtabs, sd_queue) {
+               if (__predict_false(st->sd_gone))
+                       continue;
                if (uio->uio_resid == 0)
                        return 0;
                if (uio->uio_offset <= st->sd_strsize + filepos) {