On Thu, Jan 21, 2021 at 10:37:21PM +0530, Naresh Kamboju wrote: > While running rcu-torture test on qemu_arm64 and arm64 Juno-r2 device > the following kernel crash noticed. This started happening from Linux next > next-20210111 tag to next-20210121. > > metadata: > git branch: master > git repo: https://gitlab.com/Linaro/lkft/mirrors/next/linux-next > git describe: next-20210111 > kernel-config: https://builds.tuxbuild.com/1muTTn7AfqcWvH5x2Alxifn7EUH/config > > output log: > > [ 621.538050] mem_dump_obj() slab test: rcu_torture_stats = > ffff0000c0a3ac40, &rhp = ffff800012debe40, rhp = ffff0000c8cba000, &z > = ffff8000091ab8e0 > [ 621.546662] mem_dump_obj(ZERO_SIZE_PTR): > [ 621.546696] Unable to handle kernel NULL pointer dereference at > virtual address 0000000000000008 > [ 621.555431] Mem abort info: > [ 621.557243] ESR = 0x96000006 > [ 621.559074] EC = 0x25: DABT (current EL), IL = 32 bits > [ 621.562240] SET = 0, FnV = 0 > [ 621.563626] EA = 0, S1PTW = 0 > [ 621.565134] Data abort info: > [ 621.566425] ISV = 0, ISS = 0x00000006 > [ 621.568064] CM = 0, WnR = 0 > [ 621.569571] user pgtable: 4k pages, 48-bit VAs, pgdp=0000000101ef0000 > [ 621.572446] [0000000000000008] pgd=0000000102ee1003, > p4d=0000000102ee1003, pud=0000000100b25003, pmd=0000000000000000 > [ 621.577007] Internal error: Oops: 96000006 [#1] PREEMPT SMP > [ 621.579359] Modules linked in: rcutorture(-) torture rfkill crct10dif_ce fuse > [ 621.582549] CPU: 2 PID: 422 Comm: rcu_torture_sta Not tainted > 5.11.0-rc2-next-20210111 #2 > [ 621.585294] Hardware name: linux,dummy-virt (DT) > [ 621.586671] pstate: 80000005 (Nzcv daif -PAN -UAO -TCO BTYPE=--) > [ 621.588497] pc : kmem_valid_obj+0x58/0xa8 > [ 621.589748] lr : kmem_valid_obj+0x40/0xa8 > [ 621.591022] sp : ffff800012debdc0 > [ 621.592026] x29: ffff800012debdc0 x28: 0000000000000000 > [ 621.593652] x27: ffff800012e8b988 x26: ffff0000c634dbc0 > [ 621.595287] x25: 0000000000000000 x24: ffff8000091a1e60 > [ 621.596882] x23: ffff8000091ab8e0 x22: ffff0000c0a3ac40 > [ 621.598464] x21: ffff0000c1f44100 x20: ffff8000091a5e90 > [ 621.600070] x19: 0000000000000000 x18: 0000000000000010 > [ 621.601692] x17: 0000000000007fff x16: 00000000ffffffff > [ 621.603303] x15: ffff0000c0a3b0b8 x14: 66203d2070687226 > [ 621.604866] x13: 202c303463613361 x12: 2c30346562656432 > [ 621.606455] x11: ffff80001246cbc0 x10: ffff800012454b80 > [ 621.608064] x9 : ffff8000100370c8 x8 : 0000000100000000 > [ 621.609649] x7 : 0000000000000018 x6 : ffff800012816348 > [ 621.611253] x5 : ffff800012816348 x4 : 0000000000000001 > [ 621.612849] x3 : 0000000000000001 x2 : 0000000140000000 > [ 621.614455] x1 : 0000000000000000 x0 : fffffc0000000000 > [ 621.616062] Call trace: > [ 621.616816] kmem_valid_obj+0x58/0xa8 > [ 621.617933] mem_dump_obj+0x20/0xc8 > [ 621.619015] rcu_torture_stats+0xf0/0x298 [rcutorture] > [ 621.620578] kthread+0x120/0x158 > [ 621.621583] ret_from_fork+0x10/0x34 > [ 621.622685] Code: 8b000273 b25657e0 d34cfe73 8b131813 (f9400660) > [ 621.624570] ---[ end trace 2a00688830f37ea1 ]--- > > Reported-by: Naresh Kamboju <naresh.kamboju@xxxxxxxxxx> > > Full test log: > https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20210111/testrun/3716647/suite/linux-log-parser/test/check-kernel-oops-2124993/log > https://qa-reports.linaro.org/lkft/linux-next-master/build/next-20210121/testrun/3791289/suite/linux-log-parser/test/check-kernel-oops-2172413/log Huh. I am relying on virt_addr_valid() rejecting NULL pointers and things like ZERO_SIZE_PTR, which is defined as ((void *)16). It looks like your configuration rejects NULL as an invalid virtual address, but does not reject ZERO_SIZE_PTR. Is this the intent, given that you are not allowed to dereference a ZERO_SIZE_PTR? Adding the ARM64 guys on CC for their thoughts. It is easy enough for me to make kmem_valid_obj() return false for any address less than (say) PAGE_SIZE for the upcoming merge window, but I figured I should check for the longer term. Thanx, Paul
