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authorKees Cook <keescook@chromium.org>2022-09-27 08:37:01 -0700
committerJakub Kicinski <kuba@kernel.org>2022-09-29 18:44:07 -0700
commit7cba18332e3635aaae60e4e7d4e52849de50d91b (patch)
tree8b18c900a236a5a65f6c612d0728687c5ef4abcd /net/sched
parent5361660af6d35f2b84926f5fcbf0491a9c21d82e (diff)
downloadlinux-7cba18332e3635aaae60e4e7d4e52849de50d91b.tar.bz2
net: sched: cls_u32: Avoid memcpy() false-positive warning
To work around a misbehavior of the compiler's ability to see into composite flexible array structs (as detailed in the coming memcpy() hardening series[1]), use unsafe_memcpy(), as the sizing, bounds-checking, and allocation are all very tightly coupled here. This silences the false-positive reported by syzbot: memcpy: detected field-spanning write (size 80) of single field "&n->sel" at net/sched/cls_u32.c:1043 (size 16) [1] https://lore.kernel.org/linux-hardening/20220901065914.1417829-2-keescook@chromium.org Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: Jiri Pirko <jiri@resnulli.us> Reported-by: syzbot+a2c4601efc75848ba321@syzkaller.appspotmail.com Link: https://lore.kernel.org/lkml/000000000000a96c0b05e97f0444@google.com/ Signed-off-by: Kees Cook <keescook@chromium.org> Reviewed-by: Jamal Hadi Salim <jhs@mojatatu.com> Link: https://lore.kernel.org/r/20220927153700.3071688-1-keescook@chromium.org Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/sched')
-rw-r--r--net/sched/cls_u32.c6
1 files changed, 5 insertions, 1 deletions
diff --git a/net/sched/cls_u32.c b/net/sched/cls_u32.c
index 58c7680faabd..0b3d909214b8 100644
--- a/net/sched/cls_u32.c
+++ b/net/sched/cls_u32.c
@@ -1040,7 +1040,11 @@ static int u32_change(struct net *net, struct sk_buff *in_skb,
}
#endif
- memcpy(&n->sel, s, sel_size);
+ unsafe_memcpy(&n->sel, s, sel_size,
+ /* A composite flex-array structure destination,
+ * which was correctly sized with struct_size(),
+ * bounds-checked against nla_len(), and allocated
+ * above. */);
RCU_INIT_POINTER(n->ht_up, ht);
n->handle = handle;
n->fshift = s->hmask ? ffs(ntohl(s->hmask)) - 1 : 0;