62 lines
1.8 KiB
Diff
62 lines
1.8 KiB
Diff
From 25e83c2270b2d2966c992885faed0b79be09f474 Mon Sep 17 00:00:00 2001
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From: Jeff Layton <jlayton@poochiereds.net>
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Date: Thu, 1 May 2014 11:15:16 -0400
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Subject: [PATCH] mountd: fix segfault in add_name with newer gcc compilers
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I hit a segfault in add_name with a mountd built with gcc-4.9.0. Some
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NULL pointer checks got reordered such that a pointer was dereferenced
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before checking to see whether it was NULL. The problem was due to
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nfs-utils relying on undefined behavior, which tricked gcc into assuming
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that the pointer would never be NULL.
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At first I assumed that this was a compiler bug, but Jakub Jelinek and
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Jeff Law pointed out:
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"If old is NULL, then:
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strncpy(new, old, cp-old);
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is undefined behavior (even when cp == old == NULL in that case),
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therefore gcc assumes that old is never NULL, as otherwise it would be
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invalid.
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Just guard
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strncpy(new, old, cp-old);
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new[cp-old] = 0;
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with if (old) { ... }."
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This patch does that. If old is NULL though, then we still need to
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ensure that new is NULL terminated, lest the subsequent strcats walk off
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the end of it.
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Cc: Jeff Law <law@redhat.com>
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Cc: Jakub Jelinek <jakub@redhat.com>
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Signed-off-by: Jeff Layton <jlayton@poochiereds.net>
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Signed-off-by: Steve Dickson <steved@redhat.com>
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---
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support/export/client.c | 8 ++++++--
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1 file changed, 6 insertions(+), 2 deletions(-)
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diff --git a/support/export/client.c b/support/export/client.c
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index dbf47b9..f85e11c 100644
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--- a/support/export/client.c
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+++ b/support/export/client.c
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@@ -482,8 +482,12 @@ add_name(char *old, const char *add)
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else
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cp = cp + strlen(cp);
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}
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- strncpy(new, old, cp-old);
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- new[cp-old] = 0;
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+ if (old) {
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+ strncpy(new, old, cp-old);
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+ new[cp-old] = 0;
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+ } else {
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+ new[0] = 0;
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+ }
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if (cp != old && !*cp)
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strcat(new, ",");
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strcat(new, add);
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--
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1.9.0
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