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rds_tcp_laddr_check() looks up a scoped IPv6 interface with dev_get_by_index_rcu(), drops the RCU read-side lock, and only then passes the bare struct net_device * into ipv6_chk_addr(). dev_get_by_index_rcu() only keeps the device alive within</div>
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</head><body><pre style="font-family: sans-serif; font-size: 100%; white-space: pre-wrap; word-wrap: break-word">rds_tcp_laddr_check() looks up a scoped IPv6 interface with
dev_get_by_index_rcu(), drops the RCU read-side lock, and only then
passes the bare struct net_device * into ipv6_chk_addr().
dev_get_by_index_rcu() only keeps the device alive within the same RCU
read-side section. After rcu_read_unlock(), a concurrent RTM_DELLINK can
free the net_device; ipv6_chk_addr() then dereferences the stale pointer
in __ipv6_chk_addr_and_flags() (e.g. l3mdev_master_dev_rcu(dev)), reading
freed memory.
Keep the RCU read-side lock held across the ipv6_chk_addr() call instead
of dropping it right after the lookup, so the device cannot be freed
while it is in use.
BUG: KASAN: slab-use-after-free in __ipv6_chk_addr_and_flags (... net/ipv6/addrconf.c:1998)
Read of size 8 at addr ffff8880106ec000 by task exploit/153
Call Trace:
...
kasan_report (mm/kasan/report.c:595)
__ipv6_chk_addr_and_flags (... net/ipv6/addrconf.c:1998)
ipv6_chk_addr (net/ipv6/addrconf.c:2031 net/ipv6/addrconf.c:1972)
rds_tcp_laddr_check (net/rds/tcp.c:370)
rds_bind (net/rds/bind.c:248)
__sys_bind (net/socket.c:1920)
__x64_sys_bind (net/socket.c:1956)
do_syscall_64 (arch/x86/entry/syscall_64.c:63)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)
Fixes: eee2fa6ab322 ("rds: Changing IP address internal representation to struct in6_addr")
Reported-by: Weiming Shi <bestswngs@gmail.com>
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Xiang Mei <xmei5@asu.edu>
Reviewed-by: Allison Henderson <achender@kernel.org>
---
v2: Use rcu_read_locks and rebase on rds: Fix inet6_addr_lst NULL
dereference when IPv6 is disabled
v3: Add change log to commit message as Allison suggested
v4: remove the changelog in the commit message since that was my misunderstanding
net/rds/tcp.c | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/net/rds/tcp.c b/net/rds/tcp.c
index 955d92277d5a..30cfb0087f2c 100644
--- a/net/rds/tcp.c
+++ b/net/rds/tcp.c
@@ -355,23 +355,25 @@ int rds_tcp_laddr_check(struct net *net, const struct in6_addr *addr,
/* If the scope_id is specified, check only those addresses
* hosted on the specified interface.
*/
+ rcu_read_lock();
if (scope_id != 0) {
- rcu_read_lock();
dev = dev_get_by_index_rcu(net, scope_id);
/* scope_id is not valid... */
if (!dev) {
rcu_read_unlock();
return -EADDRNOTAVAIL;
}
- rcu_read_unlock();
}
#if IS_ENABLED(CONFIG_IPV6)
if (ipv6_mod_enabled()) {
ret = ipv6_chk_addr(net, addr, dev, 0);
- if (ret)
+ if (ret) {
+ rcu_read_unlock();
return 0;
+ }
}
#endif
+ rcu_read_unlock();
return -EADDRNOTAVAIL;
}
--
2.43.0
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