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Message-ID: <20250618140844.1686882-2-edumazet@google.com>
Date: Wed, 18 Jun 2025 14:08:43 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>, syzbot+8b64dec3affaed7b3af5@...kaller.appspotmail.com
Subject: [PATCH net 1/2] net: atm: add lec_mutex
syzbot found its way in net/atm/lec.c, and found an error path
in lecd_attach() could leave a dangling pointer in dev_lec[].
Add a mutex to protect dev_lecp[] uses from lecd_attach(),
lec_vcc_attach() and lec_mcast_attach().
Following patch will use this mutex for /proc/net/atm/lec.
BUG: KASAN: slab-use-after-free in lecd_attach net/atm/lec.c:751 [inline]
BUG: KASAN: slab-use-after-free in lane_ioctl+0x2224/0x23e0 net/atm/lec.c:1008
Read of size 8 at addr ffff88807c7b8e68 by task syz.1.17/6142
CPU: 1 UID: 0 PID: 6142 Comm: syz.1.17 Not tainted 6.16.0-rc1-syzkaller-00239-g08215f5486ec #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x116/0x1f0 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:408 [inline]
print_report+0xcd/0x680 mm/kasan/report.c:521
kasan_report+0xe0/0x110 mm/kasan/report.c:634
lecd_attach net/atm/lec.c:751 [inline]
lane_ioctl+0x2224/0x23e0 net/atm/lec.c:1008
do_vcc_ioctl+0x12c/0x930 net/atm/ioctl.c:159
sock_do_ioctl+0x118/0x280 net/socket.c:1190
sock_ioctl+0x227/0x6b0 net/socket.c:1311
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl fs/ioctl.c:893 [inline]
__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
</TASK>
Allocated by task 6132:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
poison_kmalloc_redzone mm/kasan/common.c:377 [inline]
__kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:394
kasan_kmalloc include/linux/kasan.h:260 [inline]
__do_kmalloc_node mm/slub.c:4328 [inline]
__kvmalloc_node_noprof+0x27b/0x620 mm/slub.c:5015
alloc_netdev_mqs+0xd2/0x1570 net/core/dev.c:11711
lecd_attach net/atm/lec.c:737 [inline]
lane_ioctl+0x17db/0x23e0 net/atm/lec.c:1008
do_vcc_ioctl+0x12c/0x930 net/atm/ioctl.c:159
sock_do_ioctl+0x118/0x280 net/socket.c:1190
sock_ioctl+0x227/0x6b0 net/socket.c:1311
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl fs/ioctl.c:893 [inline]
__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xcd/0x4c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 6132:
kasan_save_stack+0x33/0x60 mm/kasan/common.c:47
kasan_save_track+0x14/0x30 mm/kasan/common.c:68
kasan_save_free_info+0x3b/0x60 mm/kasan/generic.c:576
poison_slab_object mm/kasan/common.c:247 [inline]
__kasan_slab_free+0x51/0x70 mm/kasan/common.c:264
kasan_slab_free include/linux/kasan.h:233 [inline]
slab_free_hook mm/slub.c:2381 [inline]
slab_free mm/slub.c:4643 [inline]
kfree+0x2b4/0x4d0 mm/slub.c:4842
free_netdev+0x6c5/0x910 net/core/dev.c:11892
lecd_attach net/atm/lec.c:744 [inline]
lane_ioctl+0x1ce8/0x23e0 net/atm/lec.c:1008
do_vcc_ioctl+0x12c/0x930 net/atm/ioctl.c:159
sock_do_ioctl+0x118/0x280 net/socket.c:1190
sock_ioctl+0x227/0x6b0 net/socket.c:1311
vfs_ioctl fs/ioctl.c:51 [inline]
__do_sys_ioctl fs/ioctl.c:907 [inline]
__se_sys_ioctl fs/ioctl.c:893 [inline]
__x64_sys_ioctl+0x18e/0x210 fs/ioctl.c:893
Fixes: da177e4c3f41 ("Linux-2.6.12-rc2")
Reported-by: syzbot+8b64dec3affaed7b3af5@...kaller.appspotmail.com
Closes: https://lore.kernel.org/netdev/6852c6f6.050a0220.216029.0018.GAE@google.com/T/#u
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
net/atm/lec.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/net/atm/lec.c b/net/atm/lec.c
index acef984f3367094ec6d30419166b8462c88181b3..1e1f3eb0e2ba3cc1caa52e49327cecb8d18250e7 100644
--- a/net/atm/lec.c
+++ b/net/atm/lec.c
@@ -124,6 +124,7 @@ static unsigned char bus_mac[ETH_ALEN] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
/* Device structures */
static struct net_device *dev_lec[MAX_LEC_ITF];
+static DEFINE_MUTEX(lec_mutex);
#if IS_ENABLED(CONFIG_BRIDGE)
static void lec_handle_bridge(struct sk_buff *skb, struct net_device *dev)
@@ -685,6 +686,7 @@ static int lec_vcc_attach(struct atm_vcc *vcc, void __user *arg)
int bytes_left;
struct atmlec_ioc ioc_data;
+ lockdep_assert_held(&lec_mutex);
/* Lecd must be up in this case */
bytes_left = copy_from_user(&ioc_data, arg, sizeof(struct atmlec_ioc));
if (bytes_left != 0)
@@ -710,6 +712,7 @@ static int lec_vcc_attach(struct atm_vcc *vcc, void __user *arg)
static int lec_mcast_attach(struct atm_vcc *vcc, int arg)
{
+ lockdep_assert_held(&lec_mutex);
if (arg < 0 || arg >= MAX_LEC_ITF)
return -EINVAL;
arg = array_index_nospec(arg, MAX_LEC_ITF);
@@ -725,6 +728,7 @@ static int lecd_attach(struct atm_vcc *vcc, int arg)
int i;
struct lec_priv *priv;
+ lockdep_assert_held(&lec_mutex);
if (arg < 0)
arg = 0;
if (arg >= MAX_LEC_ITF)
@@ -742,6 +746,7 @@ static int lecd_attach(struct atm_vcc *vcc, int arg)
snprintf(dev_lec[i]->name, IFNAMSIZ, "lec%d", i);
if (register_netdev(dev_lec[i])) {
free_netdev(dev_lec[i]);
+ dev_lec[i] = NULL;
return -EINVAL;
}
@@ -1003,6 +1008,7 @@ static int lane_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
return -ENOIOCTLCMD;
}
+ mutex_lock(&lec_mutex);
switch (cmd) {
case ATMLEC_CTRL:
err = lecd_attach(vcc, (int)arg);
@@ -1017,6 +1023,7 @@ static int lane_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
break;
}
+ mutex_unlock(&lec_mutex);
return err;
}
--
2.50.0.rc2.696.g1fc2a0284f-goog
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