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authorKuniyuki Iwashima <kuniyu@amazon.com>2023-10-09 08:31:52 -0700
committerPaolo Abeni <pabeni@redhat.com>2023-10-12 09:15:15 +0200
commite2bca4870fdaf855651ee80b083d892599c5d982 (patch)
treee7b39472334d3b0ec8b61e3f5b61846a36ce2c9e /net/packet
parent71c299c711d1f44f0bf04f1fea66baad565240f1 (diff)
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::<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>
Diffstat (limited to 'net/packet')
-rw-r--r--net/packet/af_packet.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index 8f97648d652f..a84e00b5904b 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;