From: Kuniyuki Iwashima Date: Mon, 9 Oct 2023 15:31:52 +0000 (-0700) Subject: af_packet: Fix fortified memcpy() without flex array. X-Git-Tag: v6.6.7~1748^2~3 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=e2bca4870fdaf855651ee80b083d892599c5d982;p=platform%2Fkernel%2Flinux-starfive.git af_packet: Fix fortified memcpy() without flex array. Sergei Trofimovich reported a regression [0] caused by commit a0ade8404c3b ("af_packet: Fix warning of fortified memcpy() in packet_getname()."). It introduced a flex array sll_addr_flex in struct sockaddr_ll as a union-ed member with sll_addr to work around the fortified memcpy() check. However, a userspace program uses a struct that has struct sockaddr_ll in the middle, where a flex array is illegal to exist. include/linux/if_packet.h:24:17: error: flexible array member 'sockaddr_ll::::::sll_addr_flex' not at end of 'struct packet_info_t' 24 | __DECLARE_FLEX_ARRAY(unsigned char, sll_addr_flex); | ^~~~~~~~~~~~~~~~~~~~ To fix the regression, let's go back to the first attempt [1] telling memcpy() the actual size of the array. Reported-by: Sergei Trofimovich Closes: https://github.com/NixOS/nixpkgs/pull/252587#issuecomment-1741733002 [0] Link: https://lore.kernel.org/netdev/20230720004410.87588-3-kuniyu@amazon.com/ [1] Fixes: a0ade8404c3b ("af_packet: Fix warning of fortified memcpy() in packet_getname().") Signed-off-by: Kuniyuki Iwashima Link: https://lore.kernel.org/r/20231009153151.75688-1-kuniyu@amazon.com Signed-off-by: Paolo Abeni --- diff --git a/include/uapi/linux/if_packet.h b/include/uapi/linux/if_packet.h index 4d0ad22..9efc423 100644 --- a/include/uapi/linux/if_packet.h +++ b/include/uapi/linux/if_packet.h @@ -18,11 +18,7 @@ struct sockaddr_ll { unsigned short sll_hatype; unsigned char sll_pkttype; unsigned char sll_halen; - union { - unsigned char sll_addr[8]; - /* Actual length is in sll_halen. */ - __DECLARE_FLEX_ARRAY(unsigned char, sll_addr_flex); - }; + unsigned char sll_addr[8]; }; /* Packet types */ diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c index 8f97648..a84e00b 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -3607,7 +3607,12 @@ static int packet_getname(struct socket *sock, struct sockaddr *uaddr, if (dev) { sll->sll_hatype = dev->type; sll->sll_halen = dev->addr_len; - memcpy(sll->sll_addr_flex, dev->dev_addr, dev->addr_len); + + /* Let __fortify_memcpy_chk() know the actual buffer size. */ + memcpy(((struct sockaddr_storage *)sll)->__data + + offsetof(struct sockaddr_ll, sll_addr) - + offsetofend(struct sockaddr_ll, sll_family), + dev->dev_addr, dev->addr_len); } else { sll->sll_hatype = 0; /* Bad: we have no ARPHRD_UNSPEC */ sll->sll_halen = 0;