Messages in this thread Patch in this message | | | From | Duoming Zhou <> | Subject | [Fixes] ax25: add refcount in ax25_dev to avoid UAF bugs | Date | Thu, 3 Feb 2022 00:18:46 +0800 |
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If we dereference ax25_dev after we call kfree(ax25_dev) in ax25_dev_device_down(), it will lead to concurrency UAF bugs. There are eight syscall functions suffer from UAF bugs, include ax25_bind(), ax25_release(), ax25_connect(), ax25_ioctl(), ax25_getname(), ax25_sendmsg(), ax25_getsockopt() and ax25_info_show().
One of the concurrency UAF can be shown as below:
(USE) | (FREE) | ax25_device_event | ax25_dev_device_down ax25_bind | ... ... | kfree(ax25_dev) ax25_fillin_cb() | ... ax25_fillin_cb_from_dev() | ... |
The root cause of UAF bugs is that kfree(ax25_dev) in ax25_dev_device_down() is not protected by any locks. When ax25_dev, which there are still pointers point to, is released, the concurrency UAF bug will happen.
This patch introduces refcount into ax25_dev in order to guarantee that there are no pointers point to it when ax25_dev is released.
Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> --- include/net/ax25.h | 12 ++++++++++++ net/ax25/af_ax25.c | 20 ++++++++++++++++---- net/ax25/ax25_dev.c | 33 +++++++++++++++++++++++++++------ net/ax25/ax25_route.c | 27 ++++++++++++++++++++++----- 4 files changed, 77 insertions(+), 15 deletions(-)
diff --git a/include/net/ax25.h b/include/net/ax25.h index 526e4958919..1a38b1ad529 100644 --- a/include/net/ax25.h +++ b/include/net/ax25.h @@ -239,6 +239,7 @@ typedef struct ax25_dev { #if defined(CONFIG_AX25_DAMA_SLAVE) || defined(CONFIG_AX25_DAMA_MASTER) ax25_dama_info dama; #endif + refcount_t refcount; } ax25_dev; typedef struct ax25_cb { @@ -293,6 +294,17 @@ static __inline__ void ax25_cb_put(ax25_cb *ax25) } } +static inline void ax25_dev_hold(ax25_dev *ax25_dev) +{ + refcount_inc(&ax25_dev->refcount); +} + +static inline void ax25_dev_put(ax25_dev *ax25_dev) +{ + if (refcount_dec_and_test(&ax25_dev->refcount)) + kfree(ax25_dev); +} + static inline __be16 ax25_type_trans(struct sk_buff *skb, struct net_device *dev) { skb->dev = dev; diff --git a/net/ax25/af_ax25.c b/net/ax25/af_ax25.c index 44a8730c26a..7463bbd4e63 100644 --- a/net/ax25/af_ax25.c +++ b/net/ax25/af_ax25.c @@ -91,6 +91,7 @@ static void ax25_kill_by_device(struct net_device *dev) spin_unlock_bh(&ax25_list_lock); lock_sock(sk); s->ax25_dev = NULL; + ax25_dev_put(ax25_dev); release_sock(sk); ax25_disconnect(s, ENETUNREACH); spin_lock_bh(&ax25_list_lock); @@ -358,21 +359,31 @@ static int ax25_ctl_ioctl(const unsigned int cmd, void __user *arg) if (copy_from_user(&ax25_ctl, arg, sizeof(ax25_ctl))) return -EFAULT; - if ((ax25_dev = ax25_addr_ax25dev(&ax25_ctl.port_addr)) == NULL) + ax25_dev = ax25_addr_ax25dev(&ax25_ctl.port_addr); + if (ax25_dev == NULL) { + ax25_dev_put(ax25_dev); return -ENODEV; + } - if (ax25_ctl.digi_count > AX25_MAX_DIGIS) + if (ax25_ctl.digi_count > AX25_MAX_DIGIS) { + ax25_dev_put(ax25_dev); return -EINVAL; + } - if (ax25_ctl.arg > ULONG_MAX / HZ && ax25_ctl.cmd != AX25_KILL) + if (ax25_ctl.arg > ULONG_MAX / HZ && ax25_ctl.cmd != AX25_KILL) { + ax25_dev_put(ax25_dev); return -EINVAL; + } digi.ndigi = ax25_ctl.digi_count; for (k = 0; k < digi.ndigi; k++) digi.calls[k] = ax25_ctl.digi_addr[k]; - if ((ax25 = ax25_find_cb(&ax25_ctl.source_addr, &ax25_ctl.dest_addr, &digi, ax25_dev->dev)) == NULL) + ax25 = ax25_find_cb(&ax25_ctl.source_addr, &ax25_ctl.dest_addr, &digi, ax25_dev->dev); + if (ax25 == NULL) { + ax25_dev_put(ax25_dev); return -ENOTCONN; + } switch (ax25_ctl.cmd) { case AX25_KILL: @@ -439,6 +450,7 @@ static int ax25_ctl_ioctl(const unsigned int cmd, void __user *arg) } out_put: + ax25_dev_put(ax25_dev); ax25_cb_put(ax25); return ret; diff --git a/net/ax25/ax25_dev.c b/net/ax25/ax25_dev.c index 256fadb94df..77d9aa2ccab 100644 --- a/net/ax25/ax25_dev.c +++ b/net/ax25/ax25_dev.c @@ -37,6 +37,7 @@ ax25_dev *ax25_addr_ax25dev(ax25_address *addr) for (ax25_dev = ax25_dev_list; ax25_dev != NULL; ax25_dev = ax25_dev->next) if (ax25cmp(addr, (const ax25_address *)ax25_dev->dev->dev_addr) == 0) { res = ax25_dev; + ax25_dev_hold(ax25_dev); } spin_unlock_bh(&ax25_dev_lock); @@ -56,6 +57,7 @@ void ax25_dev_device_up(struct net_device *dev) return; } + refcount_set(&ax25_dev->refcount, 1); dev->ax25_ptr = ax25_dev; ax25_dev->dev = dev; dev_hold_track(dev, &ax25_dev->dev_tracker, GFP_ATOMIC); @@ -83,6 +85,7 @@ void ax25_dev_device_up(struct net_device *dev) spin_lock_bh(&ax25_dev_lock); ax25_dev->next = ax25_dev_list; ax25_dev_list = ax25_dev; + ax25_dev_hold(ax25_dev); spin_unlock_bh(&ax25_dev_lock); ax25_register_dev_sysctl(ax25_dev); @@ -111,21 +114,23 @@ void ax25_dev_device_down(struct net_device *dev) s->forward = NULL; if ((s = ax25_dev_list) == ax25_dev) { + ax25_dev_put(ax25_dev_list); ax25_dev_list = s->next; spin_unlock_bh(&ax25_dev_lock); dev->ax25_ptr = NULL; dev_put_track(dev, &ax25_dev->dev_tracker); - kfree(ax25_dev); + ax25_dev_put(ax25_dev); return; } while (s != NULL && s->next != NULL) { if (s->next == ax25_dev) { + ax25_dev_put(s->next); s->next = ax25_dev->next; spin_unlock_bh(&ax25_dev_lock); dev->ax25_ptr = NULL; dev_put_track(dev, &ax25_dev->dev_tracker); - kfree(ax25_dev); + ax25_dev_put(ax25_dev); return; } @@ -133,31 +138,47 @@ void ax25_dev_device_down(struct net_device *dev) } spin_unlock_bh(&ax25_dev_lock); dev->ax25_ptr = NULL; + ax25_dev_put(ax25_dev); } int ax25_fwd_ioctl(unsigned int cmd, struct ax25_fwd_struct *fwd) { ax25_dev *ax25_dev, *fwd_dev; - if ((ax25_dev = ax25_addr_ax25dev(&fwd->port_from)) == NULL) + ax25_dev = ax25_addr_ax25dev(&fwd->port_from); + if (ax25_dev == NULL) { + ax25_dev_put(ax25_dev); return -EINVAL; + } switch (cmd) { case SIOCAX25ADDFWD: - if ((fwd_dev = ax25_addr_ax25dev(&fwd->port_to)) == NULL) + fwd_dev = ax25_addr_ax25dev(&fwd->port_to); + if (fwd_dev == NULL) { + ax25_dev_put(fwd_dev); + ax25_dev_put(ax25_dev); return -EINVAL; - if (ax25_dev->forward != NULL) + } + if (ax25_dev->forward != NULL) { + ax25_dev_put(ax25_dev); return -EINVAL; + } ax25_dev->forward = fwd_dev->dev; + ax25_dev_put(fwd_dev); + ax25_dev_put(ax25_dev); break; case SIOCAX25DELFWD: - if (ax25_dev->forward == NULL) + if (ax25_dev->forward == NULL) { + ax25_dev_put(ax25_dev); return -EINVAL; + } ax25_dev->forward = NULL; + ax25_dev_put(ax25_dev); break; default: + ax25_dev_put(ax25_dev); return -EINVAL; } diff --git a/net/ax25/ax25_route.c b/net/ax25/ax25_route.c index d0b2e094bd5..7fe7a83b2a3 100644 --- a/net/ax25/ax25_route.c +++ b/net/ax25/ax25_route.c @@ -75,10 +75,15 @@ static int __must_check ax25_rt_add(struct ax25_routes_struct *route) ax25_dev *ax25_dev; int i; - if ((ax25_dev = ax25_addr_ax25dev(&route->port_addr)) == NULL) + ax25_dev = ax25_addr_ax25dev(&route->port_addr); + if (ax25_dev == NULL) { + ax25_dev_put(ax25_dev); return -EINVAL; - if (route->digi_count > AX25_MAX_DIGIS) + } + if (route->digi_count > AX25_MAX_DIGIS) { + ax25_dev_put(ax25_dev); return -EINVAL; + } write_lock_bh(&ax25_route_lock); @@ -91,6 +96,7 @@ static int __must_check ax25_rt_add(struct ax25_routes_struct *route) if (route->digi_count != 0) { if ((ax25_rt->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) { write_unlock_bh(&ax25_route_lock); + ax25_dev_put(ax25_dev); return -ENOMEM; } ax25_rt->digipeat->lastrepeat = -1; @@ -101,6 +107,7 @@ static int __must_check ax25_rt_add(struct ax25_routes_struct *route) } } write_unlock_bh(&ax25_route_lock); + ax25_dev_put(ax25_dev); return 0; } ax25_rt = ax25_rt->next; @@ -108,6 +115,7 @@ static int __must_check ax25_rt_add(struct ax25_routes_struct *route) if ((ax25_rt = kmalloc(sizeof(ax25_route), GFP_ATOMIC)) == NULL) { write_unlock_bh(&ax25_route_lock); + ax25_dev_put(ax25_dev); return -ENOMEM; } @@ -120,6 +128,7 @@ static int __must_check ax25_rt_add(struct ax25_routes_struct *route) if ((ax25_rt->digipeat = kmalloc(sizeof(ax25_digi), GFP_ATOMIC)) == NULL) { write_unlock_bh(&ax25_route_lock); kfree(ax25_rt); + ax25_dev_put(ax25_dev); return -ENOMEM; } ax25_rt->digipeat->lastrepeat = -1; @@ -132,6 +141,7 @@ static int __must_check ax25_rt_add(struct ax25_routes_struct *route) ax25_rt->next = ax25_route_list; ax25_route_list = ax25_rt; write_unlock_bh(&ax25_route_lock); + ax25_dev_put(ax25_dev); return 0; } @@ -147,8 +157,11 @@ static int ax25_rt_del(struct ax25_routes_struct *route) ax25_route *s, *t, *ax25_rt; ax25_dev *ax25_dev; - if ((ax25_dev = ax25_addr_ax25dev(&route->port_addr)) == NULL) + ax25_dev = ax25_addr_ax25dev(&route->port_addr); + if (ax25_dev == NULL) { + ax25_dev_put(ax25_dev); return -EINVAL; + } write_lock_bh(&ax25_route_lock); @@ -173,7 +186,7 @@ static int ax25_rt_del(struct ax25_routes_struct *route) } } write_unlock_bh(&ax25_route_lock); - + ax25_dev_put(ax25_dev); return 0; } @@ -183,8 +196,11 @@ static int ax25_rt_opt(struct ax25_route_opt_struct *rt_option) ax25_dev *ax25_dev; int err = 0; - if ((ax25_dev = ax25_addr_ax25dev(&rt_option->port_addr)) == NULL) + ax25_dev = ax25_addr_ax25dev(&rt_option->port_addr); + if (ax25_dev == NULL) { + ax25_dev_put(ax25_dev); return -EINVAL; + } write_lock_bh(&ax25_route_lock); @@ -215,6 +231,7 @@ static int ax25_rt_opt(struct ax25_route_opt_struct *rt_option) out: write_unlock_bh(&ax25_route_lock); + ax25_dev_put(ax25_dev); return err; } -- 2.17.1
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