Messages in this thread Patch in this message | | | Date | Sun, 21 Dec 2008 14:42:18 +0100 | From | Vegard Nossum <> | Subject | [PATCH] netlink: fix (theoretical) overrun in message iteration |
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From bb805d89e84ddb11c9bb58afcfd9a6b37bbe5a9b Mon Sep 17 00:00:00 2001 From: Vegard Nossum <vegard.nossum@gmail.com> Date: Sun, 21 Dec 2008 14:20:49 +0100 Subject: [PATCH] netlink: fix (theoretical) overrun in message iteration
See commit 1045b03e07d85f3545118510a587035536030c1c for a detailed explanation of why this patch is necessary.
In short, nlmsg_next() can make "remaining" go negative, and the remaining >= sizeof(...) comparison will promote "remaining" to an unsigned type, which means that the expression will evaluate to true for negative numbers, even though it was not intended.
I put "theoretical" in the title because I have no evidence that this can actually happen, but I suspect that a crafted netlink packet can trigger some badness.
Note that the last test, which seemingly has the exact same problem (also true for nla_ok()), is perfectly OK, since we already know that remaining is positive.
Cc: Thomas Graf <tgraf@suug.ch> Signed-off-by: Vegard Nossum <vegard.nossum@gmail.com> --- include/net/netlink.h | 2 +- 1 files changed, 1 insertions(+), 1 deletions(-)
diff --git a/include/net/netlink.h b/include/net/netlink.h index 3643bbb..13dd525 100644 --- a/include/net/netlink.h +++ b/include/net/netlink.h @@ -332,7 +332,7 @@ static inline int nlmsg_attrlen(const struct nlmsghdr *nlh, int hdrlen) */ static inline int nlmsg_ok(const struct nlmsghdr *nlh, int remaining) { - return (remaining >= sizeof(struct nlmsghdr) && + return (remaining >= (int) sizeof(struct nlmsghdr) && nlh->nlmsg_len >= sizeof(struct nlmsghdr) && nlh->nlmsg_len <= remaining); } -- 1.5.6.5
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