5.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Kito Xu (veritas501) hxzene@gmail.com
[ Upstream commit 6c4a92d07b0850342d3becf2e608f805e972467c ]
The AARP proxyâprobe routine (aarp_proxy_probe_network) sends a probe, releases the aarp_lock, sleeps, then re-acquires the lock. During that window an expire timer thread (__aarp_expire_timer) can remove and kfree() the same entry, leading to a use-after-free.
race condition:
cpu 0 | cpu 1 atalk_sendmsg() | atif_proxy_probe_device() aarp_send_ddp() | aarp_proxy_probe_network() mod_timer() | lock(aarp_lock) // LOCK!! timeout around 200ms | alloc(aarp_entry) and then call | proxies[hash] = aarp_entry aarp_expire_timeout() | aarp_send_probe() | unlock(aarp_lock) // UNLOCK!! lock(aarp_lock) // LOCK!! | msleep(100); __aarp_expire_timer(&proxies[ct]) | free(aarp_entry) | unlock(aarp_lock) // UNLOCK!! | | lock(aarp_lock) // LOCK!! | UAF aarp_entry !!
================================================================== BUG: KASAN: slab-use-after-free in aarp_proxy_probe_network+0x560/0x630 net/appletalk/aarp.c:493 Read of size 4 at addr ffff8880123aa360 by task repro/13278
CPU: 3 UID: 0 PID: 13278 Comm: repro Not tainted 6.15.2 #3 PREEMPT(full) Call Trace: <TASK> __dump_stack lib/dump_stack.c:94 [inline] dump_stack_lvl+0x116/0x1b0 lib/dump_stack.c:120 print_address_description mm/kasan/report.c:408 [inline] print_report+0xc1/0x630 mm/kasan/report.c:521 kasan_report+0xca/0x100 mm/kasan/report.c:634 aarp_proxy_probe_network+0x560/0x630 net/appletalk/aarp.c:493 atif_proxy_probe_device net/appletalk/ddp.c:332 [inline] atif_ioctl+0xb58/0x16c0 net/appletalk/ddp.c:857 atalk_ioctl+0x198/0x2f0 net/appletalk/ddp.c:1818 sock_do_ioctl+0xdc/0x260 net/socket.c:1190 sock_ioctl+0x239/0x6a0 net/socket.c:1311 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:906 [inline] __se_sys_ioctl fs/ioctl.c:892 [inline] __x64_sys_ioctl+0x194/0x200 fs/ioctl.c:892 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline] do_syscall_64+0xcb/0x250 arch/x86/entry/syscall_64.c:94 entry_SYSCALL_64_after_hwframe+0x77/0x7f </TASK>
Allocated: aarp_alloc net/appletalk/aarp.c:382 [inline] aarp_proxy_probe_network+0xd8/0x630 net/appletalk/aarp.c:468 atif_proxy_probe_device net/appletalk/ddp.c:332 [inline] atif_ioctl+0xb58/0x16c0 net/appletalk/ddp.c:857 atalk_ioctl+0x198/0x2f0 net/appletalk/ddp.c:1818
Freed: kfree+0x148/0x4d0 mm/slub.c:4841 __aarp_expire net/appletalk/aarp.c:90 [inline] __aarp_expire_timer net/appletalk/aarp.c:261 [inline] aarp_expire_timeout+0x480/0x6e0 net/appletalk/aarp.c:317
The buggy address belongs to the object at ffff8880123aa300 which belongs to the cache kmalloc-192 of size 192 The buggy address is located 96 bytes inside of freed 192-byte region [ffff8880123aa300, ffff8880123aa3c0)
Memory state around the buggy address: ffff8880123aa200: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff8880123aa280: 00 00 00 00 fc fc fc fc fc fc fc fc fc fc fc fc
ffff8880123aa300: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^ ffff8880123aa380: fb fb fb fb fb fb fb fb fc fc fc fc fc fc fc fc ffff8880123aa400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ==================================================================
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Kito Xu (veritas501) hxzene@gmail.com Link: https://patch.msgid.link/20250717012843.880423-1-hxzene@gmail.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/appletalk/aarp.c | 24 +++++++++++++++++++++--- 1 file changed, 21 insertions(+), 3 deletions(-)
diff --git a/net/appletalk/aarp.c b/net/appletalk/aarp.c index be18af481d7d5..17d9cb380e7bd 100644 --- a/net/appletalk/aarp.c +++ b/net/appletalk/aarp.c @@ -35,6 +35,7 @@ #include <linux/seq_file.h> #include <linux/export.h> #include <linux/etherdevice.h> +#include <linux/refcount.h>
int sysctl_aarp_expiry_time = AARP_EXPIRY_TIME; int sysctl_aarp_tick_time = AARP_TICK_TIME; @@ -44,6 +45,7 @@ int sysctl_aarp_resolve_time = AARP_RESOLVE_TIME; /* Lists of aarp entries */ /** * struct aarp_entry - AARP entry + * @refcnt: Reference count * @last_sent: Last time we xmitted the aarp request * @packet_queue: Queue of frames wait for resolution * @status: Used for proxy AARP @@ -55,6 +57,7 @@ int sysctl_aarp_resolve_time = AARP_RESOLVE_TIME; * @next: Next entry in chain */ struct aarp_entry { + refcount_t refcnt; /* These first two are only used for unresolved entries */ unsigned long last_sent; struct sk_buff_head packet_queue; @@ -79,6 +82,17 @@ static DEFINE_RWLOCK(aarp_lock); /* Used to walk the list and purge/kick entries. */ static struct timer_list aarp_timer;
+static inline void aarp_entry_get(struct aarp_entry *a) +{ + refcount_inc(&a->refcnt); +} + +static inline void aarp_entry_put(struct aarp_entry *a) +{ + if (refcount_dec_and_test(&a->refcnt)) + kfree(a); +} + /* * Delete an aarp queue * @@ -87,7 +101,7 @@ static struct timer_list aarp_timer; static void __aarp_expire(struct aarp_entry *a) { skb_queue_purge(&a->packet_queue); - kfree(a); + aarp_entry_put(a); }
/* @@ -380,9 +394,11 @@ static void aarp_purge(void) static struct aarp_entry *aarp_alloc(void) { struct aarp_entry *a = kmalloc(sizeof(*a), GFP_ATOMIC); + if (!a) + return NULL;
- if (a) - skb_queue_head_init(&a->packet_queue); + refcount_set(&a->refcnt, 1); + skb_queue_head_init(&a->packet_queue); return a; }
@@ -508,6 +524,7 @@ int aarp_proxy_probe_network(struct atalk_iface *atif, struct atalk_addr *sa) entry->dev = atif->dev;
write_lock_bh(&aarp_lock); + aarp_entry_get(entry);
hash = sa->s_node % (AARP_HASH_SIZE - 1); entry->next = proxies[hash]; @@ -533,6 +550,7 @@ int aarp_proxy_probe_network(struct atalk_iface *atif, struct atalk_addr *sa) retval = 1; }
+ aarp_entry_put(entry); write_unlock_bh(&aarp_lock); out: return retval;