6.5-stable review patch. If anyone has any objections, please let me know.
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From: Kuniyuki Iwashima kuniyu@amazon.com
[ Upstream commit e2bca4870fdaf855651ee80b083d892599c5d982 ]
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::<unnamed union>::<unnamed struct>::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 slyich@gmail.com 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 kuniyu@amazon.com Link: https://lore.kernel.org/r/20231009153151.75688-1-kuniyu@amazon.com Signed-off-by: Paolo Abeni pabeni@redhat.com Signed-off-by: Sasha Levin sashal@kernel.org --- include/uapi/linux/if_packet.h | 6 +----- net/packet/af_packet.c | 7 ++++++- 2 files changed, 7 insertions(+), 6 deletions(-)
diff --git a/include/uapi/linux/if_packet.h b/include/uapi/linux/if_packet.h index 4d0ad22f83b56..9efc42382fdb9 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 a2935bd18ed98..a39b2a0dd5425 100644 --- a/net/packet/af_packet.c +++ b/net/packet/af_packet.c @@ -3605,7 +3605,12 @@ 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;