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Violators will be prosecuted for from ; Tue, 16 May 2017 14:01:21 +1000 Received: from d23av04.au.ibm.com (d23av04.au.ibm.com [9.190.235.139]) by d23relay07.au.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id v4G41Bp155640076 for ; Tue, 16 May 2017 14:01:19 +1000 Received: from d23av04.au.ibm.com (localhost [127.0.0.1]) by d23av04.au.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id v4G40jx7010738 for ; Tue, 16 May 2017 14:00:45 +1000 Subject: Re: kernel BUG at mm/usercopy.c:72! To: Breno Leitao , linuxppc-dev@lists.ozlabs.org References: <20170515191949.GA13641@gmail.com> Cc: gromero@br.ibm.com From: Anshuman Khandual Date: Tue, 16 May 2017 09:30:27 +0530 MIME-Version: 1.0 In-Reply-To: <20170515191949.GA13641@gmail.com> Content-Type: text/plain; charset=windows-1252 Message-Id: <53dcd142-47d6-f6c0-32b1-a5d611810873@linux.vnet.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On 05/16/2017 12:49 AM, Breno Leitao wrote: > Hello, > > Kernel 4.12-rc1 is showing a bug when I try it on a POWER8 virtual > machine. Justing SSHing into the machine causes this issue. > > [23.138124] usercopy: kernel memory overwrite attempt detected to d000000003d80030 (mm_struct) (560 bytes) > [23.138195] ------------[ cut here ]------------ > [23.138229] kernel BUG at mm/usercopy.c:72! > [23.138252] Oops: Exception in kernel mode, sig: 5 [#3] > [23.138280] SMP NR_CPUS=2048 > [23.138280] NUMA > [23.138302] pSeries > [23.138330] Modules linked in: > [23.138354] CPU: 4 PID: 2215 Comm: sshd Tainted: G D 4.12.0-rc1+ #9 > [23.138395] task: c0000001e272dc00 task.stack: c0000001e27b0000 > [23.138430] NIP: c000000000342358 LR: c000000000342354 CTR: c0000000006eb060 > [23.138472] REGS: c0000001e27b3a00 TRAP: 0700 Tainted: G D (4.12.0-rc1+) > [23.138513] MSR: 8000000000029033 > [23.138517] CR: 28004222 XER: 20000000 > [23.138565] CFAR: c000000000b34500 SOFTE: 1 > [23.138565] GPR00: c000000000342354 c0000001e27b3c80 c00000000142a000 000000000000005e > [23.138565] GPR04: c0000001ffe0ade8 c0000001ffe21bf8 2920283536302062 79746573290d0a74 > [23.138565] GPR08: 0000000000000007 c000000000f61864 00000001feeb0000 3064206f74206465 > [23.138565] GPR12: 0000000000004400 c00000000fb42600 0000000000000015 00000000545bdc40 > [23.138565] GPR16: 00000000545c49c8 000001000b4b8890 00007ffff78c26f0 00000000545cf000 > [23.138565] GPR20: 00000000546109c8 000000000000c7e8 0000000054610010 00007ffff78c22e8 > [23.138565] GPR24: 00000000545c8c40 c0000000ff6bcef0 c0000000001e5220 0000000000000230 > [23.138565] GPR28: d000000003d80260 0000000000000000 0000000000000230 d000000003d80030 > [23.138920] NIP [c000000000342358] __check_object_size+0x88/0x2d0 > [23.138956] LR [c000000000342354] __check_object_size+0x84/0x2d0 > [23.138990] Call Trace: > [23.139006] [c0000001e27b3c80] [c000000000342354] __check_object_size+0x84/0x2d0 (unreliable) > [23.139056] [c0000001e27b3d00] [c0000000009f5ba8] bpf_prog_create_from_user+0xa8/0x1a0 > [23.139099] [c0000001e27b3d60] [c0000000001e5d30] do_seccomp+0x120/0x720 > [23.139136] [c0000001e27b3dd0] [c0000000000fd53c] SyS_prctl+0x2ac/0x6b0 > [23.139172] [c0000001e27b3e30] [c00000000000af84] system_call+0x38/0xe0 > [23.139218] Instruction dump: > [23.139240] 60000000 60420000 3c82ff94 3ca2ff9d 38841788 38a5e868 3c62ff95 7fc8f378 > [23.139283] 7fe6fb78 386310c0 487f2169 60000000 <0fe00000> 60420000 2ba30010 409d018c > [23.139328] ---[ end trace 1a1dc952a4b7c4af ]--- > > I found that kernel 4.11 does not have this issue. I also found that, if > I revert 517e1fbeb65f5eade8d14f46ac365db6c75aea9b, I do not see the > problem. commit 517e1fbeb65f5eade8d14f46ac365db6c75aea9b Author: Laura Abbott Date: Tue Apr 4 14:09:00 2017 -0700 mm/usercopy: Drop extra is_vmalloc_or_module() check Previously virt_addr_valid() was insufficient to validate if virt_to_page() could be called on an address on arm64. This has since been fixed up so there is no need for the extra check. Drop it. Signed-off-by: Laura Abbott Acked-by: Mark Rutland Signed-off-by: Kees Cook diff --git a/mm/usercopy.c b/mm/usercopy.c index 1eba99b..a9852b2 100644 --- a/mm/usercopy.c +++ b/mm/usercopy.c @@ -200,17 +200,6 @@ static inline const char *check_heap_object(const void *ptr, unsigned long n, { struct page *page; - /* - * Some architectures (arm64) return true for virt_addr_valid() on - * vmalloced addresses. Work around this by checking for vmalloc - * first. - * - * We also need to check for module addresses explicitly since we - * may copy static data from modules to userspace - */ - if (is_vmalloc_or_module_addr(ptr)) - return NULL; - if (!virt_addr_valid(ptr)) return NULL; On POWER8 (CONFIG_PPC64), #define virt_addr_valid(kaddr) pfn_valid(virt_to_pfn(kaddr)) #define virt_to_pfn(kaddr) (__pa(kaddr) >> PAGE_SHIFT) #define __pa(x) ((unsigned long)(x) & 0x0fffffffffffffffUL) Hence some vmalloc (0xd range) addresses can still pass the virt_addr_valid() test, hence the removed exclusive check for vmalloc and module addresses in the commit is still required for powerpc. If that is the case, we should revert the commit. - Anshuman