6.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
[ 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@xxxxxxxxx>
Closes: https://github.com/NixOS/nixpkgs/pull/252587#issuecomment-1741733002 [0]
Link: https://lore.kernel.org/netdev/20230720004410.87588-3-kuniyu@xxxxxxxxxx/ [1]
Fixes: a0ade8404c3b ("af_packet: Fix warning of fortified memcpy() in packet_getname().")
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20231009153151.75688-1-kuniyu@xxxxxxxxxx
Signed-off-by: Paolo Abeni <pabeni@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
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;
--
2.40.1
