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linux-user: fix off-by-one in host_to_target_for_each_rtattr()

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host_to_target_for_each_rtattr() uses "len > sizeof(struct rtattr)"
as its loop condition. When the last rtattr in a netlink message has
exactly sizeof(struct rtattr) (4) bytes remaining, the loop exits
without byte-swapping its rta_len and rta_type. A big-endian guest
then reads rta_len in the wrong byte order and fails validation.

The companion function target_to_host_for_each_rtattr() correctly
uses ">=" (added in commit fa2229dbf8). The kernel's RTA_OK macro
also uses ">=". Fix the host_to_target direction to match.

Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2485
Signed-off-by: Yixin Wei <yixinwei@meta.com>
Fixes: 6c5b5645ae ("linux-user: add rtnetlink(7) support")
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Signed-off-by: Helge Deller <deller@gmx.de>
Cc: qemu-stable@nongnu.org
This commit is contained in:
Yixin Wei
2026-04-09 17:49:38 +01:00
committed by Helge Deller
parent 654dce6c52
commit 029f10e852
1 changed files with 1 additions and 1 deletions
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2
linux-user/fd-trans.c
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@@ -480,7 +480,7 @@ static abi_long host_to_target_for_each_rtattr(struct rtattr *rtattr,
unsigned short aligned_rta_len; unsigned short aligned_rta_len;
abi_long ret; abi_long ret;
while (len > sizeof(struct rtattr)) { while (len >= sizeof(struct rtattr)) {
rta_len = rtattr->rta_len; rta_len = rtattr->rta_len;
if (rta_len < sizeof(struct rtattr) || if (rta_len < sizeof(struct rtattr) ||
rta_len > len) { rta_len > len) {