| Message ID | 20210708080532.74526-1-xuanzhuo@linux.alibaba.com (mailing list archive) |
|---|---|
| State | Superseded |
| Delegated to: | BPF |
| Headers | show |
| Series | [net] xdp, net: fix use-after-free in bpf_xdp_link_release | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | fail | Series targets non-next tree, but doesn't contain any Fixes tags |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for net |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | success | CCed 18 of 18 maintainers |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 6 this patch: 6 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 39 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 6 this patch: 6 |
| netdev/header_inline | success | Link |
On Thu, Jul 8, 2021 at 1:05 AM Xuan Zhuo <xuanzhuo@linux.alibaba.com> wrote: > > The problem occurs between dev_get_by_index() and dev_xdp_attach_link(). > At this point in time, the xdp link will not be released automatically > when dev is deleted. In this way, when xdp link is released, dev will > still be accessed, but dev has been released. Do I understand correctly that the problem is that between when get dev with dev_get_by_index() and by the time we call dev_xdp_attach_link() to record bpf_link inside dev we might get a call to dev_xdp_uninstall(dev). At that point we missed the notification that dev is going away but we still succeed to attach bpf_link. Do I understand the situation correctly? If yes, I wonder whether the proper fix would be to make sure that if the device was removed bpf_xdp_link_attach() will return an error. That seems like a sane behavior, instead of pretending that attachment succeeded. At that point we should NULL out link->dev and cleanup bpf_xdp_link. > > [ 45.966867] BUG: KASAN: use-after-free in bpf_xdp_link_release+0x3b8/0x3d0 > [ 45.967619] Read of size 8 at addr ffff00000f9980c8 by task a.out/732 > [ 45.968297] > [ 45.968502] CPU: 1 PID: 732 Comm: a.out Not tainted 5.13.0+ #22 > [ 45.969222] Hardware name: linux,dummy-virt (DT) > [ 45.969795] Call trace: > [ 45.970106] dump_backtrace+0x0/0x4c8 > [ 45.970564] show_stack+0x30/0x40 > [ 45.970981] dump_stack_lvl+0x120/0x18c > [ 45.971470] print_address_description.constprop.0+0x74/0x30c > [ 45.972182] kasan_report+0x1e8/0x200 > [ 45.972659] __asan_report_load8_noabort+0x2c/0x50 > [ 45.973273] bpf_xdp_link_release+0x3b8/0x3d0 > [ 45.973834] bpf_link_free+0xd0/0x188 > [ 45.974315] bpf_link_put+0x1d0/0x218 > [ 45.974790] bpf_link_release+0x3c/0x58 > [ 45.975291] __fput+0x20c/0x7e8 > [ 45.975706] ____fput+0x24/0x30 > [ 45.976117] task_work_run+0x104/0x258 > [ 45.976609] do_notify_resume+0x894/0xaf8 > [ 45.977121] work_pending+0xc/0x328 > [ 45.977575] > [ 45.977775] The buggy address belongs to the page: > [ 45.978369] page:fffffc00003e6600 refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x4f998 > [ 45.979522] flags: 0x7fffe0000000000(node=0|zone=0|lastcpupid=0x3ffff) > [ 45.980349] raw: 07fffe0000000000 fffffc00003e6708 ffff0000dac3c010 0000000000000000 > [ 45.981309] raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 > [ 45.982259] page dumped because: kasan: bad access detected > [ 45.982948] > [ 45.983153] Memory state around the buggy address: > [ 45.983753] ffff00000f997f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc > [ 45.984645] ffff00000f998000: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > [ 45.985533] >ffff00000f998080: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > [ 45.986419] ^ > [ 45.987112] ffff00000f998100: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > [ 45.988006] ffff00000f998180: ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff ff > [ 45.988895] ================================================================== > [ 45.989773] Disabling lock debugging due to kernel taint > [ 45.990552] Kernel panic - not syncing: panic_on_warn set ... > [ 45.991166] CPU: 1 PID: 732 Comm: a.out Tainted: G B 5.13.0+ #22 > [ 45.991929] Hardware name: linux,dummy-virt (DT) > [ 45.992448] Call trace: > [ 45.992753] dump_backtrace+0x0/0x4c8 > [ 45.993208] show_stack+0x30/0x40 > [ 45.993627] dump_stack_lvl+0x120/0x18c > [ 45.994113] dump_stack+0x1c/0x34 > [ 45.994530] panic+0x3a4/0x7d8 > [ 45.994930] end_report+0x194/0x198 > [ 45.995380] kasan_report+0x134/0x200 > [ 45.995850] __asan_report_load8_noabort+0x2c/0x50 > [ 45.996453] bpf_xdp_link_release+0x3b8/0x3d0 > [ 45.997007] bpf_link_free+0xd0/0x188 > [ 45.997474] bpf_link_put+0x1d0/0x218 > [ 45.997942] bpf_link_release+0x3c/0x58 > [ 45.998429] __fput+0x20c/0x7e8 > [ 45.998833] ____fput+0x24/0x30 > [ 45.999247] task_work_run+0x104/0x258 > [ 45.999731] do_notify_resume+0x894/0xaf8 > [ 46.000236] work_pending+0xc/0x328 > [ 46.000697] SMP: stopping secondary CPUs > [ 46.001226] Dumping ftrace buffer: > [ 46.001663] (ftrace buffer empty) > [ 46.002110] Kernel Offset: disabled > [ 46.002545] CPU features: 0x00000001,23202c00 > [ 46.003080] Memory Limit: none > > Reported-by: Abaci <abaci@linux.alibaba.com> > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> > Reviewed-by: Dust Li <dust.li@linux.alibaba.com> > --- > net/core/dev.c | 13 +++++++++---- > 1 file changed, 9 insertions(+), 4 deletions(-) > > diff --git a/net/core/dev.c b/net/core/dev.c > index c253c2aafe97..f7aba3108016 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -9684,14 +9684,17 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) > struct net_device *dev; > int err, fd; > > + rtnl_lock(); > dev = dev_get_by_index(net, attr->link_create.target_ifindex); > - if (!dev) > + if (!dev) { > + rtnl_unlock(); > return -EINVAL; > + } > > link = kzalloc(sizeof(*link), GFP_USER); > if (!link) { > err = -ENOMEM; > - goto out_put_dev; > + goto unlock_put_dev; > } > > bpf_link_init(&link->link, BPF_LINK_TYPE_XDP, &bpf_xdp_link_lops, prog); > @@ -9701,10 +9704,9 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) > err = bpf_link_prime(&link->link, &link_primer); > if (err) { > kfree(link); > - goto out_put_dev; > + goto unlock_put_dev; > } > > - rtnl_lock(); > err = dev_xdp_attach_link(dev, NULL, link); > rtnl_unlock(); > > @@ -9718,6 +9720,9 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) > dev_put(dev); > return fd; > > +unlock_put_dev: > + rtnl_unlock(); > + > out_put_dev: > dev_put(dev); > return err; > -- > 2.31.0 >
diff --git a/net/core/dev.c b/net/core/dev.c index c253c2aafe97..f7aba3108016 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -9684,14 +9684,17 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) struct net_device *dev; int err, fd; + rtnl_lock(); dev = dev_get_by_index(net, attr->link_create.target_ifindex); - if (!dev) + if (!dev) { + rtnl_unlock(); return -EINVAL; + } link = kzalloc(sizeof(*link), GFP_USER); if (!link) { err = -ENOMEM; - goto out_put_dev; + goto unlock_put_dev; } bpf_link_init(&link->link, BPF_LINK_TYPE_XDP, &bpf_xdp_link_lops, prog); @@ -9701,10 +9704,9 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) err = bpf_link_prime(&link->link, &link_primer); if (err) { kfree(link); - goto out_put_dev; + goto unlock_put_dev; } - rtnl_lock(); err = dev_xdp_attach_link(dev, NULL, link); rtnl_unlock(); @@ -9718,6 +9720,9 @@ int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) dev_put(dev); return fd; +unlock_put_dev: + rtnl_unlock(); + out_put_dev: dev_put(dev); return err;