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Sat, 6 Feb 2021 02:56:39 +0000 (GMT) Received: from skywalker.ibmuc.com (unknown [9.85.72.86]) by b03ledav002.gho.boulder.ibm.com (Postfix) with ESMTP; Sat, 6 Feb 2021 02:56:38 +0000 (GMT) From: "Aneesh Kumar K.V" To: linuxppc-dev@lists.ozlabs.org, mpe@ellerman.id.au Subject: [PATCH v3] powerpc/kuap: Allow kernel thread to access userspace after kthread_use_mm Date: Sat, 6 Feb 2021 08:26:34 +0530 Message-Id: <20210206025634.521979-1-aneesh.kumar@linux.ibm.com> X-Mailer: git-send-email 2.29.2 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.369, 18.0.737 definitions=2021-02-05_15:2021-02-05, 2021-02-05 signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 phishscore=0 mlxlogscore=999 clxscore=1015 bulkscore=0 malwarescore=0 adultscore=0 impostorscore=0 lowpriorityscore=0 spamscore=0 mlxscore=0 priorityscore=1501 suspectscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2102060010 X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Jens Axboe , "Aneesh Kumar K.V" , Zorro Lang , Nicholas Piggin Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" This fix the bad fault reported by KUAP when io_wqe_worker access userspace. Bug: Read fault blocked by KUAP! WARNING: CPU: 1 PID: 101841 at arch/powerpc/mm/fault.c:229 __do_page_fault+0x6b4/0xcd0 NIP [c00000000009e7e4] __do_page_fault+0x6b4/0xcd0 LR [c00000000009e7e0] __do_page_fault+0x6b0/0xcd0 .......... Call Trace: [c000000016367330] [c00000000009e7e0] __do_page_fault+0x6b0/0xcd0 (unreliable) [c0000000163673e0] [c00000000009ee3c] do_page_fault+0x3c/0x120 [c000000016367430] [c00000000000c848] handle_page_fault+0x10/0x2c --- interrupt: 300 at iov_iter_fault_in_readable+0x148/0x6f0 .......... NIP [c0000000008e8228] iov_iter_fault_in_readable+0x148/0x6f0 LR [c0000000008e834c] iov_iter_fault_in_readable+0x26c/0x6f0 interrupt: 300 [c0000000163677e0] [c0000000007154a0] iomap_write_actor+0xc0/0x280 [c000000016367880] [c00000000070fc94] iomap_apply+0x1c4/0x780 [c000000016367990] [c000000000710330] iomap_file_buffered_write+0xa0/0x120 [c0000000163679e0] [c00800000040791c] xfs_file_buffered_aio_write+0x314/0x5e0 [xfs] [c000000016367a90] [c0000000006d74bc] io_write+0x10c/0x460 [c000000016367bb0] [c0000000006d80e4] io_issue_sqe+0x8d4/0x1200 [c000000016367c70] [c0000000006d8ad0] io_wq_submit_work+0xc0/0x250 [c000000016367cb0] [c0000000006e2578] io_worker_handle_work+0x498/0x800 [c000000016367d40] [c0000000006e2cdc] io_wqe_worker+0x3fc/0x4f0 [c000000016367da0] [c0000000001cb0a4] kthread+0x1c4/0x1d0 [c000000016367e10] [c00000000000dbf0] ret_from_kernel_thread+0x5c/0x6c The kernel consider thread AMR value for kernel thread to be AMR_KUAP_BLOCKED. Hence access to userspace is denied. This of course not correct and we should allow userspace access after kthread_use_mm(). To be precise, kthread_use_mm() should inherit the AMR value of the operating address space. But, the AMR value is thread-specific and we inherit the address space and not thread access restrictions. Because of this ignore AMR value when accessing userspace via kernel thread. current_thread_amr/iamr() are updated, because we use them in the below stack. .... [ 530.710838] CPU: 13 PID: 5587 Comm: io_wqe_worker-0 Tainted: G D 5.11.0-rc6+ #3 .... NIP [c0000000000aa0c8] pkey_access_permitted+0x28/0x90 LR [c0000000004b9278] gup_pte_range+0x188/0x420 --- interrupt: 700 [c00000001c4ef3f0] [0000000000000000] 0x0 (unreliable) [c00000001c4ef490] [c0000000004bd39c] gup_pgd_range+0x3ac/0xa20 [c00000001c4ef5a0] [c0000000004bdd44] internal_get_user_pages_fast+0x334/0x410 [c00000001c4ef620] [c000000000852028] iov_iter_get_pages+0xf8/0x5c0 [c00000001c4ef6a0] [c0000000007da44c] bio_iov_iter_get_pages+0xec/0x700 [c00000001c4ef770] [c0000000006a325c] iomap_dio_bio_actor+0x2ac/0x4f0 [c00000001c4ef810] [c00000000069cd94] iomap_apply+0x2b4/0x740 [c00000001c4ef920] [c0000000006a38b8] __iomap_dio_rw+0x238/0x5c0 [c00000001c4ef9d0] [c0000000006a3c60] iomap_dio_rw+0x20/0x80 [c00000001c4ef9f0] [c008000001927a30] xfs_file_dio_aio_write+0x1f8/0x650 [xfs] [c00000001c4efa60] [c0080000019284dc] xfs_file_write_iter+0xc4/0x130 [xfs] [c00000001c4efa90] [c000000000669984] io_write+0x104/0x4b0 [c00000001c4efbb0] [c00000000066cea4] io_issue_sqe+0x3d4/0xf50 [c00000001c4efc60] [c000000000670200] io_wq_submit_work+0xb0/0x2f0 [c00000001c4efcb0] [c000000000674268] io_worker_handle_work+0x248/0x4a0 [c00000001c4efd30] [c0000000006746e8] io_wqe_worker+0x228/0x2a0 [c00000001c4efda0] [c00000000019d994] kthread+0x1b4/0x1c0 Cc: Zorro Lang Cc: Jens Axboe Cc: Christophe Leroy Cc: Nicholas Piggin Signed-off-by: Aneesh Kumar K.V --- Changes from v2: * Fix build error Changes from v1: * use default_amr/default_iamr for kthread. arch/powerpc/include/asm/book3s/64/kup.h | 16 +++++++++++----- arch/powerpc/include/asm/book3s/64/pkeys.h | 4 ---- arch/powerpc/mm/book3s64/pkeys.c | 1 + 3 files changed, 12 insertions(+), 9 deletions(-) diff --git a/arch/powerpc/include/asm/book3s/64/kup.h b/arch/powerpc/include/asm/book3s/64/kup.h index f50f72e535aa..7d1ef7b9754e 100644 --- a/arch/powerpc/include/asm/book3s/64/kup.h +++ b/arch/powerpc/include/asm/book3s/64/kup.h @@ -199,25 +199,31 @@ DECLARE_STATIC_KEY_FALSE(uaccess_flush_key); #ifdef CONFIG_PPC_PKEY +extern u64 __ro_after_init default_uamor; +extern u64 __ro_after_init default_amr; +extern u64 __ro_after_init default_iamr; + #include #include -/* - * For kernel thread that doesn't have thread.regs return - * default AMR/IAMR values. +/* usage of kthread_use_mm() should inherit the + * AMR value of the operating address space. But, the AMR value is + * thread-specific and we inherit the address space and not thread + * access restrictions. Because of this ignore AMR value when accessing + * userspace via kernel thread. */ static inline u64 current_thread_amr(void) { if (current->thread.regs) return current->thread.regs->amr; - return AMR_KUAP_BLOCKED; + return default_amr; } static inline u64 current_thread_iamr(void) { if (current->thread.regs) return current->thread.regs->iamr; - return AMR_KUEP_BLOCKED; + return default_iamr; } #endif /* CONFIG_PPC_PKEY */ diff --git a/arch/powerpc/include/asm/book3s/64/pkeys.h b/arch/powerpc/include/asm/book3s/64/pkeys.h index 3b8640498f5b..5b178139f3c0 100644 --- a/arch/powerpc/include/asm/book3s/64/pkeys.h +++ b/arch/powerpc/include/asm/book3s/64/pkeys.h @@ -5,10 +5,6 @@ #include -extern u64 __ro_after_init default_uamor; -extern u64 __ro_after_init default_amr; -extern u64 __ro_after_init default_iamr; - static inline u64 vmflag_to_pte_pkey_bits(u64 vm_flags) { if (!mmu_has_feature(MMU_FTR_PKEY)) diff --git a/arch/powerpc/mm/book3s64/pkeys.c b/arch/powerpc/mm/book3s64/pkeys.c index f1c6f264ed91..15dcc5ad91c5 100644 --- a/arch/powerpc/mm/book3s64/pkeys.c +++ b/arch/powerpc/mm/book3s64/pkeys.c @@ -31,6 +31,7 @@ static u32 initial_allocation_mask __ro_after_init; u64 default_amr __ro_after_init = ~0x0UL; u64 default_iamr __ro_after_init = 0x5555555555555555UL; u64 default_uamor __ro_after_init; +EXPORT_SYMBOL(default_amr); /* * Key used to implement PROT_EXEC mmap. Denies READ/WRITE * We pick key 2 because 0 is special key and 1 is reserved as per ISA. -- 2.29.2