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Re: Segfault in getifaddrs_internal in glibc-2.20
- From: Andreas Schwab <schwab at linux-m68k dot org>
- To: Allan McRae <allan at archlinux dot org>
- Cc: libc-alpha <libc-alpha at sourceware dot org>
- Date: Sat, 13 Sep 2014 10:18:20 +0200
- Subject: Re: Segfault in getifaddrs_internal in glibc-2.20
- Authentication-results: sourceware.org; auth=none
- References: <5413EA84 dot 3060901 at archlinux dot org>
Allan McRae <allan@archlinux.org> writes:
> diff --git a/sysdeps/unix/sysv/linux/ifaddrs.c
> b/sysdeps/unix/sysv/linux/ifaddrs.c
> index 2c04e17..1fa4960 100644
> --- a/sysdeps/unix/sysv/linux/ifaddrs.c
> +++ b/sysdeps/unix/sysv/linux/ifaddrs.c
> @@ -774,7 +774,7 @@ getifaddrs_internal (struct ifaddrs **ifap)
> unsigned int preflen;
>
> if ((max_prefixlen > 0) &&
> - (ifam->ifa_prefixlen > max_prefixlen))
> + (max_prefixlen > ifam->ifa_prefixlen))
> preflen = max_prefixlen;
> else
> preflen = ifam->ifa_prefixlen;
>
>
> This seems to fix the issue for them. After looking at the code for a
> long time, I am still not sure if this is the correct fix. Can anyone
> confirm/deny?
That doesn't make any sense. As the name says, max_prefixlen is the
limit for the prefix length, but this makes it always equal to
max_prefixlen (which is always > 0 here). The bug is of course that
commit d89b3d8 doesn't handle a prefix length of zero.
Andreas.
[BZ #17371]
* sysdeps/unix/sysv/linux/ifaddrs.c (getifaddrs_internal): Fix
last change to handle zero prefix length.
---
sysdeps/unix/sysv/linux/ifaddrs.c | 11 ++++-------
1 file changed, 4 insertions(+), 7 deletions(-)
diff --git a/sysdeps/unix/sysv/linux/ifaddrs.c b/sysdeps/unix/sysv/linux/ifaddrs.c
index 2c04e17..a47b2ed 100644
--- a/sysdeps/unix/sysv/linux/ifaddrs.c
+++ b/sysdeps/unix/sysv/linux/ifaddrs.c
@@ -770,20 +770,17 @@ getifaddrs_internal (struct ifaddrs **ifap)
if (cp != NULL)
{
- char c;
unsigned int preflen;
- if ((max_prefixlen > 0) &&
- (ifam->ifa_prefixlen > max_prefixlen))
+ if (ifam->ifa_prefixlen > max_prefixlen)
preflen = max_prefixlen;
else
preflen = ifam->ifa_prefixlen;
- for (i = 0; i < ((preflen - 1) / 8); i++)
+ for (i = 0; i < preflen / 8; i++)
*cp++ = 0xff;
- c = 0xff;
- c <<= ((128 - preflen) % 8);
- *cp = c;
+ if (preflen % 8)
+ *cp = 0xff << (8 - preflen % 8);
}
}
}
--
2.1.0
--
Andreas Schwab, schwab@linux-m68k.org
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."