Messages in this thread | | | From | Jens Wiklander <> | Date | Fri, 7 May 2021 11:23:17 +0200 | Subject | Re: [PATCH] optee: Disable shm cache when booting the crash kernel |
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On Fri, May 7, 2021 at 9:00 AM Allen Pais <apais@linux.microsoft.com> wrote: > > > > > On 07-May-2021, at 9:28 AM, Tyler Hicks <tyhicks@linux.microsoft.com> wrote: > > > > The .shutdown hook is not called after a kernel crash when a kdump > > kernel is pre-loaded. A kexec into the kdump kernel takes place as > > quickly as possible without allowing drivers to clean up. > > > > That means that the OP-TEE shared memory cache, which was initialized by > > the kernel that crashed, is still in place when the kdump kernel is > > booted. As the kdump kernel is shutdown, the .shutdown hook is called, > > which calls optee_disable_shm_cache(), and OP-TEE's > > OPTEE_SMC_DISABLE_SHM_CACHE API returns virtual addresses that are not > > mapped for the kdump kernel since the cache was set up by the previous > > kernel. Trying to dereference the tee_shm pointer or otherwise translate > > the address results in a fault that cannot be handled: > > > > Unable to handle kernel paging request at virtual address ffff4317b9c09744 > > Mem abort info: > > ESR = 0x96000004 > > EC = 0x25: DABT (current EL), IL = 32 bits > > SET = 0, FnV = 0 > > EA = 0, S1PTW = 0 > > Data abort info: > > ISV = 0, ISS = 0x00000004 > > CM = 0, WnR = 0 > > swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000970b1e000 > > [ffff4317b9c09744] pgd=0000000000000000, p4d=0000000000000000 > > Internal error: Oops: 96000004 [#1] SMP > > Modules linked in: bnxt_en pcie_iproc_platform pcie_iproc diagbe(O) > > CPU: 4 PID: 1 Comm: systemd-shutdow Tainted: G O 5.10.19.8 #1 > > Hardware name: Redacted (DT) > > pstate: 60400005 (nZCv daif +PAN -UAO -TCO BTYPE=--) > > pc : tee_shm_free (/usr/src/kernel/drivers/tee/tee_shm.c:363) > > lr : optee_disable_shm_cache (/usr/src/kernel/drivers/tee/optee/call.c:441) > > sp : ffff80001005bb70 > > x29: ffff80001005bb70 x28: ffff608e74648e00 > > x27: ffff80001005bb98 x26: dead000000000100 > > x25: ffff80001005bbb8 x24: aaaaaaaaaaaaaaaa > > x23: ffff608e74cf8818 x22: ffff608e738be600 > > x21: ffff80001005bbc8 x20: ffff608e738be638 > > x19: ffff4317b9c09700 x18: ffffffffffffffff > > x17: 0000000000000041 x16: ffffba61b5171764 > > x15: 0000000000000004 x14: 0000000000000fff > > x13: ffffba61b5c9dfc8 x12: 0000000000000003 > > x11: 0000000000000000 x10: 0000000000000000 > > x9 : ffffba61b5413824 x8 : 00000000ffff4317 > > x7 : 0000000000000000 x6 : 0000000000000000 > > x5 : 0000000000000000 x4 : 0000000000000000 > > x3 : 0000000000000000 x2 : ffff4317b9c09700 > > x1 : 00000000ffff4317 x0 : ffff4317b9c09700 > > Call trace: > > tee_shm_free (/usr/src/kernel/drivers/tee/tee_shm.c:363) > > optee_disable_shm_cache (/usr/src/kernel/drivers/tee/optee/call.c:441) > > optee_shutdown (/usr/src/kernel/drivers/tee/optee/core.c:636) > > platform_drv_shutdown (/usr/src/kernel/drivers/base/platform.c:800) > > device_shutdown (/usr/src/kernel/include/linux/device.h:758 /usr/src/kernel/drivers/base/core.c:4078) > > kernel_restart (/usr/src/kernel/kernel/reboot.c:221 /usr/src/kernel/kernel/reboot.c:248) > > __arm64_sys_reboot (/usr/src/kernel/kernel/reboot.c:349 /usr/src/kernel/kernel/reboot.c:312 /usr/src/kernel/kernel/reboot.c:312) > > do_el0_svc (/usr/src/kernel/arch/arm64/kernel/syscall.c:56 /usr/src/kernel/arch/arm64/kernel/syscall.c:158 /usr/src/kernel/arch/arm64/kernel/syscall.c:197) > > el0_svc (/usr/src/kernel/arch/arm64/kernel/entry-common.c:368) > > el0_sync_handler (/usr/src/kernel/arch/arm64/kernel/entry-common.c:428) > > el0_sync (/usr/src/kernel/arch/arm64/kernel/entry.S:671) > > Code: aa0003f3 b5000060 12800003 14000002 (b9404663) > > > > When booting the kdump kernel, drain the shared memory cache while being > > careful to not translate the addresses returned from > > OPTEE_SMC_DISABLE_SHM_CACHE. Once the invalid cache objects are drained > > and the cache is disabled, proceed with re-enabling the cache so that we > > aren't dealing with invalid addresses while shutting down the kdump > > kernel. > > > > Signed-off-by: Tyler Hicks <tyhicks@linux.microsoft.com> > > --- > > > > This patch fixes a crash introduced by "optee: fix tee out of memory > > failure seen during kexec reboot"[1]. However, I don't think that the > > original two patch series[2] plus this patch is the full solution to > > properly handling OP-TEE shared memory across kexec. > > > > While testing this fix, I did about 10 kexec reboots and then triggered > > a kernel crash by writing 'c' to /proc/sysrq-trigger. The kdump kernel > > became unresponsive during boot while steadily streaming the following > > errors to the serial console: > > > > arm-smmu 64000000.mmu: Blocked unknown Stream ID 0x2000; boot with "arm-smmu.disable_bypass=0" to allow, but this may have security implications > > arm-smmu 64000000.mmu: GFSR 0x00000002, GFSYNR0 0x00000002, GFSYNR1 0x00002000, GFSYNR2 0x00000000 > > > > I suspect that this is related to the problems of OP-TEE shared memory > > handling across kexec. My current hunch is that while we've disabled the > > shared memory cache with this patch, we haven't unregistered all of the > > addresses that the previous kernel (which crashed) had registered with > > OP-TEE and that perhaps OP-TEE OS is still trying to make use those > > addresses? > > > > I'm still pretty early in investigating that assumption and > > I'm learning about OP-TEE as I go but I wanted to get this initial > > fix-of-the-fix out so that it was clear that the v2 of the series[2] is > > not complete. > > > > [1] https://lore.kernel.org/lkml/20210225090610.242623-2-allen.lkml@gmail.com/ > > [2] https://lore.kernel.org/lkml/20210225090610.242623-1-allen.lkml@gmail.com/#t > > > > drivers/tee/optee/call.c | 11 ++++++++++- > > drivers/tee/optee/core.c | 13 +++++++++++-- > > drivers/tee/optee/optee_private.h | 2 +- > > 3 files changed, 22 insertions(+), 4 deletions(-) > > > > diff --git a/drivers/tee/optee/call.c b/drivers/tee/optee/call.c > > index 6132cc8d014c..799e84bec63d 100644 > > --- a/drivers/tee/optee/call.c > > +++ b/drivers/tee/optee/call.c > > @@ -417,8 +417,10 @@ void optee_enable_shm_cache(struct optee *optee) > > * optee_disable_shm_cache() - Disables caching of some shared memory allocation > > * in OP-TEE > > * @optee: main service struct > > + * @is_mapped: true if the cached shared memory addresses were mapped by this > > + * kernel, are safe to dereference, and should be freed > > */ > > -void optee_disable_shm_cache(struct optee *optee) > > +void optee_disable_shm_cache(struct optee *optee, bool is_mapped) > > { > > struct optee_call_waiter w; > > > > @@ -437,6 +439,13 @@ void optee_disable_shm_cache(struct optee *optee) > > if (res.result.status == OPTEE_SMC_RETURN_OK) { > > struct tee_shm *shm; > > > > Thanks Tyler. > From what I understand from my email exchange with Jens, I don’t > Think we want to touch optee_disable_shm_cache(), I could be wrong too, > @Jens, comments?
Changing optee_disable_shm_cache() is fine. Bear in mind that there are other times where we can't recover from a kernel crash. For instance if a thread is executing in OP-TEE in secure world.
Cheers, Jens
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