| Message ID | 20220510080105.126146-1-michael@allwinnertech.com |
|---|---|
| State | New |
| Headers | show |
| Series | usb: f_fs: Fix crash during gadget function switching | expand |
On Tue, May 10, 2022 at 04:01:05PM +0800, Michael Wu wrote: > On arm64 android12 and possibly other platforms, during the usb gadget > function switching procedure (e.g. from mtp to midi), a synchronization > issue could occur, which causes an use-after-free panic as shown below: > > [ 119.787946][ T1] init: Control message: Processed ctl.start for 'adbd' from pid: 395 (system_server) > [ 119.790006][ T32] android_work: sent uevent USB_STATE=DISCONNECTED > [ 119.805457][ T2309] usercopy: Kernel memory exposure attempt detected from SLUB object 'kmalloc-512' (offset 0, size 1802201963)! > [ 119.819368][ T2309] ------------[ cut here ]------------ > [ 119.825359][ T2309] kernel BUG at mm/usercopy.c:99! > [ 119.830868][ T2309] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP > [ 119.837843][ T2309] Modules linked in: sunxi_usbc ohci_sunxi ehci_sunxi sunxi_hci mali_kbase(O) sunxi_rfkill > [ 119.848904][ T2309] CPU: 3 PID: 2309 Comm: MtpServer Tainted: G O 5.4.125+ #9 > [ 119.858411][ T2309] Hardware name: sun50iw9 (DT) > [ 119.863615][ T2309] pstate: 60400005 (nZCv daif +PAN -UAO) > [ 119.869790][ T2309] pc : usercopy_abort+0x90/0x94 > [ 119.875078][ T2309] lr : usercopy_abort+0x90/0x94 > [ 119.880357][ T2309] sp : ffffffc019e13ad0 > [ 119.884858][ T2309] x29: ffffffc019e13ae0 x28: 0000000000000000 > [ 119.891601][ T2309] x27: ffffff8030e7c030 x26: 0000000000000000 > [ 119.898347][ T2309] x25: 0000000000000001 x24: ffffff806e25bd30 > [ 119.905092][ T2309] x23: 000000006b6b6b6b x22: ffffff807c804680 > [ 119.911838][ T2309] x21: ffffff8041410200 x20: 0000000000000001 > [ 119.918581][ T2309] x19: 000000006b6b6b6b x18: ffffffc019e05058 > [ 119.925326][ T2309] x17: 0000000000000000 x16: 00000000000002e3 > [ 119.932073][ T2309] x15: 0000000000000000 x14: 0000000000000010 > [ 119.938820][ T2309] x13: ffffffc0103972c0 x12: 0000000000000001 > [ 119.945565][ T2309] x11: 0000000000000000 x10: 0000000000000002 > [ 119.952311][ T2309] x9 : 54fea1fa84857d00 x8 : 54fea1fa84857d00 > [ 119.959056][ T2309] x7 : 0000000000000001 x6 : 0000000000000000 > [ 119.965801][ T2309] x5 : ffffff807f3a9038 x4 : 0000000000000000 > [ 119.972546][ T2309] x3 : 0000000000000000 x2 : ffffff807f3a8f40 > [ 119.979293][ T2309] x1 : ffffffc0114e94de x0 : 000000000000006d > [ 119.986038][ T2309] Call trace: > [ 119.989569][ T2309] usercopy_abort+0x90/0x94 > [ 119.994466][ T2309] __check_heap_object+0x16c/0x188 > [ 120.000041][ T2309] __check_object_size+0x120/0x210 > [ 120.005620][ T2309] ffs_epfile_io+0x574/0x6bc > [ 120.010612][ T2309] ffs_epfile_read_iter+0x10c/0x198 > [ 120.016284][ T2309] __vfs_read+0x178/0x1e0 > [ 120.020980][ T2309] vfs_read+0x1d0/0x284 > [ 120.025481][ T2309] ksys_read+0x74/0xe0 > [ 120.029884][ T2309] __arm64_sys_read+0x1c/0x28 > [ 120.034977][ T2309] el0_svc_common+0xb8/0x1cc > [ 120.039967][ T2309] el0_svc_compat_handler+0x1c/0x28 > [ 120.045649][ T2309] el0_svc_compat+0x8/0x24 > [ 120.050453][ T2309] Code: f90003e4 aa0803e1 aa0903e4 97fa0fa9 (d4210000) > [ 120.058109][ T2309] ---[ end trace a246be823ca7d164 ]--- > [ 120.064073][ T2309] Kernel panic - not syncing: Fatal exception > [ 120.070723][ T2309] SMP: stopping secondary CPUs > [ 120.076030][ T2309] Kernel Offset: disabled > [ 120.080757][ T2309] CPU features: 0x00010002,20002004 > [ 120.086438][ T2309] Memory Limit: none > [ 120.090657][ T2309] ---[ end Kernel panic - not syncing: Fatal exception ]--- > > Two processes P1 and P2 engaged in the switching procedure: > - P1 (e.g. MtpServer) calls 'ffs_epfile_io' (alias 'C'), > - P2 (e.g. usb@1.0-service) calls 'ffs_epfile_io_complete' (alias 'A') > and the 'ffs_func_unbind' (alias 'B'). > > P1 P2 > | | > | configfs_write_file| > | gadget_dev_desc_UDC_store| > | unregister_gadget| > | usb_gadget_unregister_driver| > | usb_gadget_remove_driver| > | | > | |________________________________________ > | | | > | usb_gadget_disconnect| | > | sunxi_udc_pullup| | > | sunxi_udc_set_pullup| | > | configfs_composite_disconnect| | > | composite_disconnect| | > | reset_config| | > | ffs_func_disable| | > | ffs_func_set_alt| | > | ffs_func_eps_disable| | > | usb_ep_disable| | > | sunxi_udc_ep_disable| | > | sunxi_udc_nuke| configfs_composite_unbind| > | sunxi_udc_done| | > | | | > |ffs_epfile_read_iter | purge_configs_funcs| > | | | > | complete | | > |ffs_epfile_io [C] <------------ |ffs_epfile_io_complete [A] | I assume this is the path through ffs_epfile_io() with !io_data->aio. It looks like there is no check there for epfile->ep == ep which the other paths do check. Does the patch below fix the problem without needing to add a new completion? -- >8 -- --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -1084,16 +1084,22 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data) */ usb_ep_dequeue(ep->ep, req); wait_for_completion(&done); - interrupted = ep->status < 0; + interrupted = true; } - if (interrupted) + spin_lock_irq(&epfile->ffs->eps_lock); + if (epfile->ep != ep) + ret = -ESHUTDOWN; + else if (interrupted && ep->status < 0) ret = -EINTR; - else if (io_data->read && ep->status > 0) - ret = __ffs_epfile_read_data(epfile, data, ep->status, - &io_data->data); else ret = ep->status; + spin_unlock_irq(&epfile->ffs->eps_lock); + + if (io_data->read && ret > 0) + ret = __ffs_epfile_read_data(epfile, data, ret, + &io_data->data); + goto error_mutex; } else if (!(req = usb_ep_alloc_request(ep->ep, GFP_ATOMIC))) { ret = -ENOMEM;
On 5/31/2022 2:14 AM, John Keeping wrote: > On Tue, May 10, 2022 at 04:01:05PM +0800, Michael Wu wrote: >> On arm64 android12 and possibly other platforms, during the usb gadget >> function switching procedure (e.g. from mtp to midi), a synchronization >> issue could occur, which causes an use-after-free panic as shown below: > > I assume this is the path through ffs_epfile_io() with !io_data->aio. > It looks like there is no check there for epfile->ep == ep which the > other paths do check. > > Does the patch below fix the problem without needing to add a new > completion? > Hi John, Thanks for your suggestion. I've tested your patch and it did work -- When my issue occurs, (epfile->ep != ep) is satisfied, and the error is handled. > -- >8 -- > --- a/drivers/usb/gadget/function/f_fs.c > +++ b/drivers/usb/gadget/function/f_fs.c > @@ -1084,16 +1084,22 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data) > */ > usb_ep_dequeue(ep->ep, req); > wait_for_completion(&done); > - interrupted = ep->status < 0; > + interrupted = true; > } > > - if (interrupted) > + spin_lock_irq(&epfile->ffs->eps_lock); > + if (epfile->ep != ep) > + ret = -ESHUTDOWN; > + else if (interrupted && ep->status < 0) > ret = -EINTR; > - else if (io_data->read && ep->status > 0) > - ret = __ffs_epfile_read_data(epfile, data, ep->status, > - &io_data->data); > else > ret = ep->status; > + spin_unlock_irq(&epfile->ffs->eps_lock); > + > + if (io_data->read && ret > 0) > + ret = __ffs_epfile_read_data(epfile, data, ret, > + &io_data->data); > + > goto error_mutex; > } else if (!(req = usb_ep_alloc_request(ep->ep, GFP_ATOMIC))) { > ret = -ENOMEM; Tested-by: Michael Wu <michael@allwinnertech.com> I also tested Linyu's patch [1][2]. It also works. Is there a preference on these solutions? [1] https://lore.kernel.org/linux-usb/1654056916-2062-2-git-send-email-quic_linyyuan@quicinc.com/ [2] https://lore.kernel.org/linux-usb/1654056916-2062-3-git-send-email-quic_linyyuan@quicinc.com/
On Thu, Jun 02, 2022 at 06:36:47PM +0800, Michael Wu wrote: > On 5/31/2022 2:14 AM, John Keeping wrote: > > On Tue, May 10, 2022 at 04:01:05PM +0800, Michael Wu wrote: > > > On arm64 android12 and possibly other platforms, during the usb gadget > > > function switching procedure (e.g. from mtp to midi), a synchronization > > > issue could occur, which causes an use-after-free panic as shown below: > > > > I assume this is the path through ffs_epfile_io() with !io_data->aio. > > It looks like there is no check there for epfile->ep == ep which the > > other paths do check. > > > > Does the patch below fix the problem without needing to add a new > > completion? > > > > Hi John, > Thanks for your suggestion. I've tested your patch and it did work -- When > my issue occurs, (epfile->ep != ep) is satisfied, and the error is handled. > > > -- >8 -- > > --- a/drivers/usb/gadget/function/f_fs.c > > +++ b/drivers/usb/gadget/function/f_fs.c > > @@ -1084,16 +1084,22 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data) > > */ > > usb_ep_dequeue(ep->ep, req); > > wait_for_completion(&done); > > - interrupted = ep->status < 0; > > + interrupted = true; > > } > > - if (interrupted) > > + spin_lock_irq(&epfile->ffs->eps_lock); > > + if (epfile->ep != ep) > > + ret = -ESHUTDOWN; > > + else if (interrupted && ep->status < 0) > > ret = -EINTR; > > - else if (io_data->read && ep->status > 0) > > - ret = __ffs_epfile_read_data(epfile, data, ep->status, > > - &io_data->data); > > else > > ret = ep->status; > > + spin_unlock_irq(&epfile->ffs->eps_lock); > > + > > + if (io_data->read && ret > 0) > > + ret = __ffs_epfile_read_data(epfile, data, ret, > > + &io_data->data); > > + > > goto error_mutex; > > } else if (!(req = usb_ep_alloc_request(ep->ep, GFP_ATOMIC))) { > > ret = -ENOMEM; > Tested-by: Michael Wu <michael@allwinnertech.com> > > > I also tested Linyu's patch [1][2]. It also works. > Is there a preference on these solutions? Linyu's patch is more complete and covers some cases that I missed with this attempt, so let's drop this thread and focus on that series.
diff --git a/drivers/usb/gadget/function/f_fs.c b/drivers/usb/gadget/function/f_fs.c index 4585ee3a444a8..c3e918cd00170 100644 --- a/drivers/usb/gadget/function/f_fs.c +++ b/drivers/usb/gadget/function/f_fs.c @@ -124,6 +124,7 @@ struct ffs_ep { u8 num; int status; /* P: epfile->mutex */ + void *context; }; struct ffs_epfile { @@ -246,6 +247,7 @@ ffs_sb_create_file(struct super_block *sb, const char *name, void *data, DEFINE_MUTEX(ffs_lock); EXPORT_SYMBOL_GPL(ffs_lock); +DECLARE_COMPLETION(io_done); static struct ffs_dev *_ffs_find_dev(const char *name); static struct ffs_dev *_ffs_alloc_dev(void); @@ -711,6 +713,8 @@ static void ffs_epfile_io_complete(struct usb_ep *_ep, struct usb_request *req) if (req->context) { struct ffs_ep *ep = _ep->driver_data; ep->status = req->status ? req->status : req->actual; + if (ep->status == -ESHUTDOWN) + ep->context = &io_done; complete(req->context); } } @@ -1094,6 +1098,10 @@ static ssize_t ffs_epfile_io(struct file *file, struct ffs_io_data *io_data) &io_data->data); else ret = ep->status; + + if (ep->status == -ESHUTDOWN && ep->context) + complete(ep->context); + goto error_mutex; } else if (!(req = usb_ep_alloc_request(ep->ep, GFP_ATOMIC))) { ret = -ENOMEM; @@ -3607,6 +3615,12 @@ static void ffs_func_unbind(struct usb_configuration *c, /* cleanup after autoconfig */ spin_lock_irqsave(&func->ffs->eps_lock, flags); while (count--) { + if (ep->status == -ESHUTDOWN && ep->context) { + spin_unlock_irqrestore(&func->ffs->eps_lock, flags); + wait_for_completion(ep->context); + spin_lock_irqsave(&func->ffs->eps_lock, flags); + } + if (ep->ep && ep->req) usb_ep_free_request(ep->ep, ep->req); ep->req = NULL;
On arm64 android12 and possibly other platforms, during the usb gadget function switching procedure (e.g. from mtp to midi), a synchronization issue could occur, which causes an use-after-free panic as shown below: [ 119.787946][ T1] init: Control message: Processed ctl.start for 'adbd' from pid: 395 (system_server) [ 119.790006][ T32] android_work: sent uevent USB_STATE=DISCONNECTED [ 119.805457][ T2309] usercopy: Kernel memory exposure attempt detected from SLUB object 'kmalloc-512' (offset 0, size 1802201963)! [ 119.819368][ T2309] ------------[ cut here ]------------ [ 119.825359][ T2309] kernel BUG at mm/usercopy.c:99! [ 119.830868][ T2309] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP [ 119.837843][ T2309] Modules linked in: sunxi_usbc ohci_sunxi ehci_sunxi sunxi_hci mali_kbase(O) sunxi_rfkill [ 119.848904][ T2309] CPU: 3 PID: 2309 Comm: MtpServer Tainted: G O 5.4.125+ #9 [ 119.858411][ T2309] Hardware name: sun50iw9 (DT) [ 119.863615][ T2309] pstate: 60400005 (nZCv daif +PAN -UAO) [ 119.869790][ T2309] pc : usercopy_abort+0x90/0x94 [ 119.875078][ T2309] lr : usercopy_abort+0x90/0x94 [ 119.880357][ T2309] sp : ffffffc019e13ad0 [ 119.884858][ T2309] x29: ffffffc019e13ae0 x28: 0000000000000000 [ 119.891601][ T2309] x27: ffffff8030e7c030 x26: 0000000000000000 [ 119.898347][ T2309] x25: 0000000000000001 x24: ffffff806e25bd30 [ 119.905092][ T2309] x23: 000000006b6b6b6b x22: ffffff807c804680 [ 119.911838][ T2309] x21: ffffff8041410200 x20: 0000000000000001 [ 119.918581][ T2309] x19: 000000006b6b6b6b x18: ffffffc019e05058 [ 119.925326][ T2309] x17: 0000000000000000 x16: 00000000000002e3 [ 119.932073][ T2309] x15: 0000000000000000 x14: 0000000000000010 [ 119.938820][ T2309] x13: ffffffc0103972c0 x12: 0000000000000001 [ 119.945565][ T2309] x11: 0000000000000000 x10: 0000000000000002 [ 119.952311][ T2309] x9 : 54fea1fa84857d00 x8 : 54fea1fa84857d00 [ 119.959056][ T2309] x7 : 0000000000000001 x6 : 0000000000000000 [ 119.965801][ T2309] x5 : ffffff807f3a9038 x4 : 0000000000000000 [ 119.972546][ T2309] x3 : 0000000000000000 x2 : ffffff807f3a8f40 [ 119.979293][ T2309] x1 : ffffffc0114e94de x0 : 000000000000006d [ 119.986038][ T2309] Call trace: [ 119.989569][ T2309] usercopy_abort+0x90/0x94 [ 119.994466][ T2309] __check_heap_object+0x16c/0x188 [ 120.000041][ T2309] __check_object_size+0x120/0x210 [ 120.005620][ T2309] ffs_epfile_io+0x574/0x6bc [ 120.010612][ T2309] ffs_epfile_read_iter+0x10c/0x198 [ 120.016284][ T2309] __vfs_read+0x178/0x1e0 [ 120.020980][ T2309] vfs_read+0x1d0/0x284 [ 120.025481][ T2309] ksys_read+0x74/0xe0 [ 120.029884][ T2309] __arm64_sys_read+0x1c/0x28 [ 120.034977][ T2309] el0_svc_common+0xb8/0x1cc [ 120.039967][ T2309] el0_svc_compat_handler+0x1c/0x28 [ 120.045649][ T2309] el0_svc_compat+0x8/0x24 [ 120.050453][ T2309] Code: f90003e4 aa0803e1 aa0903e4 97fa0fa9 (d4210000) [ 120.058109][ T2309] ---[ end trace a246be823ca7d164 ]--- [ 120.064073][ T2309] Kernel panic - not syncing: Fatal exception [ 120.070723][ T2309] SMP: stopping secondary CPUs [ 120.076030][ T2309] Kernel Offset: disabled [ 120.080757][ T2309] CPU features: 0x00010002,20002004 [ 120.086438][ T2309] Memory Limit: none [ 120.090657][ T2309] ---[ end Kernel panic - not syncing: Fatal exception ]--- Two processes P1 and P2 engaged in the switching procedure: - P1 (e.g. MtpServer) calls 'ffs_epfile_io' (alias 'C'), - P2 (e.g. usb@1.0-service) calls 'ffs_epfile_io_complete' (alias 'A') and the 'ffs_func_unbind' (alias 'B'). P1 P2 | | | configfs_write_file| | gadget_dev_desc_UDC_store| | unregister_gadget| | usb_gadget_unregister_driver| | usb_gadget_remove_driver| | | | |________________________________________ | | | | usb_gadget_disconnect| | | sunxi_udc_pullup| | | sunxi_udc_set_pullup| | | configfs_composite_disconnect| | | composite_disconnect| | | reset_config| | | ffs_func_disable| | | ffs_func_set_alt| | | ffs_func_eps_disable| | | usb_ep_disable| | | sunxi_udc_ep_disable| | | sunxi_udc_nuke| configfs_composite_unbind| | sunxi_udc_done| | | | | |ffs_epfile_read_iter | purge_configs_funcs| | | | | complete | | |ffs_epfile_io [C] <------------ |ffs_epfile_io_complete [A] | | + | | | + | | + | | + [1] complete | | +++++++++++++++++++++++++++++++++++++++++++++++> ffs_func_unbind[B]| | | On gadget switching, 'A' will raise a completion, which wakes up 'P1' to resume 'C'. Then 'C' references 'ep->status' for branch jumping etc. On the other path, 'B' keeps running and exec 'kfree(func->eps)', which actually free 'ep->status' referenced by 'C'. This leads to the panic: `usercopy: Kernel memory exposure attempt detected from SLUB object 'kmalloc-512' (offset 0, size 1802201963)!` To fix this issue, we add a completion[1] to ensure that 'C' completes before 'B'. Signed-off-by: Michael Wu <michael@allwinnertech.com> --- drivers/usb/gadget/function/f_fs.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)