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e2391a2dca
When loading a patch module on a kernel with !CONFIG_DEBUG_SET_MODULE_RONX, the following crash occurs: [ 205.988776] livepatch: enabling patch 'kpatch_meminfo_string' [ 205.989829] BUG: unable to handle kernel paging request at ffffffffa08d2fc0 [ 205.989863] IP: [<ffffffff8154fecb>] do_init_module+0x8c/0x1ba [ 205.989888] PGD 1a10067 PUD 1a11063 PMD 7bcde067 PTE 3740e161 [ 205.989915] Oops: 0003 [#1] SMP [ 205.990187] CPU: 2 PID: 14570 Comm: insmod Tainted: G O K 4.1.12 [ 205.990214] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.8.1-20150318_183358- 04/01/2014 [ 205.990249] task: ffff8800374aaa90 ti: ffff8800794b8000 task.ti: ffff8800794b8000 [ 205.990276] RIP: 0010:[<ffffffff8154fecb>] [<ffffffff8154fecb>] do_init_module+0x8c/0x1ba [ 205.990307] RSP: 0018:ffff8800794bbd58 EFLAGS: 00010246 [ 205.990327] RAX: 0000000000000000 RBX: ffffffffa08d2fc0 RCX: 0000000000000000 [ 205.990356] RDX: 01ffff8000000080 RSI: 0000000000000000 RDI: ffffffff81a54b40 [ 205.990382] RBP: ffff88007b4c4d80 R08: 0000000000000007 R09: 0000000000000000 [ 205.990408] R10: 0000000000000008 R11: ffffea0001f18840 R12: 0000000000000000 [ 205.990433] R13: 0000000000000001 R14: ffffffffa08d2fc0 R15: ffff88007bd0bc40 [ 205.990459] FS: 00007f1128fbc700(0000) GS:ffff88007fc80000(0000) knlGS:0000000000000000 [ 205.990488] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 205.990509] CR2: ffffffffa08d2fc0 CR3: 000000002606e000 CR4: 00000000001406e0 [ 205.990536] Stack: [ 205.990545] ffff8800794bbec8 0000000000000001 ffffffffa08d3010 ffffffff810ecea9 [ 205.990576] ffffffff810e8e40 000000000005f360 ffff88007bd0bc50 ffffffffa08d3240 [ 205.990608] ffffffffa08d52c0 ffffffffa08d3210 ffff8800794bbed8 ffff8800794bbf1c [ 205.990639] Call Trace: [ 205.990651] [<ffffffff810ecea9>] ? load_module+0x1e59/0x23a0 [ 205.990672] [<ffffffff810e8e40>] ? store_uevent+0x40/0x40 [ 205.990693] [<ffffffff810e99b5>] ? copy_module_from_fd.isra.49+0xb5/0x140 [ 205.990718] [<ffffffff810ed5bd>] ? SyS_finit_module+0x7d/0xa0 [ 205.990741] [<ffffffff81556832>] ? system_call_fastpath+0x16/0x75 [ 205.990763] Code: f9 00 00 00 74 23 49 c7 c0 92 e1 60 81 48 8d 53 18 89 c1 4c 89 c6 48 c7 c7 f0 85 7d 81 31 c0 e8 71 fa ff ff e8 58 0e 00 00 31 f6 <c7> 03 00 00 00 00 48 89 da 48 c7 c7 20 c7 a5 81 e8 d0 ec b3 ff [ 205.990916] RIP [<ffffffff8154fecb>] do_init_module+0x8c/0x1ba [ 205.990940] RSP <ffff8800794bbd58> [ 205.990953] CR2: ffffffffa08d2fc0 With !CONFIG_DEBUG_SET_MODULE_RONX, module text and rodata pages are writable, and the debug_align() macro allows the module struct to share a page with executable text. When klp_write_module_reloc() calls set_memory_ro() on the page, it effectively turns the module struct into a read-only structure, resulting in a page fault when load_module() does "mod->state = MODULE_STATE_LIVE". Reported-by: Cyril B. <cbay@alwaysdata.com> Tested-by: Cyril B. <cbay@alwaysdata.com> Signed-off-by: Josh Poimboeuf <jpoimboe@redhat.com> Signed-off-by: Jiri Kosina <jkosina@suse.cz>
92 lines
2.4 KiB
C
92 lines
2.4 KiB
C
/*
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* livepatch.c - x86-specific Kernel Live Patching Core
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*
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* Copyright (C) 2014 Seth Jennings <sjenning@redhat.com>
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* Copyright (C) 2014 SUSE
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see <http://www.gnu.org/licenses/>.
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*/
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#include <linux/module.h>
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#include <linux/uaccess.h>
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#include <asm/cacheflush.h>
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#include <asm/page_types.h>
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#include <asm/elf.h>
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#include <asm/livepatch.h>
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/**
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* klp_write_module_reloc() - write a relocation in a module
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* @mod: module in which the section to be modified is found
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* @type: ELF relocation type (see asm/elf.h)
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* @loc: address that the relocation should be written to
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* @value: relocation value (sym address + addend)
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*
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* This function writes a relocation to the specified location for
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* a particular module.
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*/
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int klp_write_module_reloc(struct module *mod, unsigned long type,
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unsigned long loc, unsigned long value)
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{
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int ret, numpages, size = 4;
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bool readonly;
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unsigned long val;
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unsigned long core = (unsigned long)mod->module_core;
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unsigned long core_size = mod->core_size;
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switch (type) {
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case R_X86_64_NONE:
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return 0;
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case R_X86_64_64:
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val = value;
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size = 8;
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break;
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case R_X86_64_32:
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val = (u32)value;
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break;
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case R_X86_64_32S:
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val = (s32)value;
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break;
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case R_X86_64_PC32:
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val = (u32)(value - loc);
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break;
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default:
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/* unsupported relocation type */
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return -EINVAL;
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}
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if (loc < core || loc >= core + core_size)
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/* loc does not point to any symbol inside the module */
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return -EINVAL;
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readonly = false;
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#ifdef CONFIG_DEBUG_SET_MODULE_RONX
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if (loc < core + mod->core_ro_size)
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readonly = true;
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#endif
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/* determine if the relocation spans a page boundary */
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numpages = ((loc & PAGE_MASK) == ((loc + size) & PAGE_MASK)) ? 1 : 2;
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if (readonly)
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set_memory_rw(loc & PAGE_MASK, numpages);
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ret = probe_kernel_write((void *)loc, &val, size);
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if (readonly)
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set_memory_ro(loc & PAGE_MASK, numpages);
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return ret;
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}
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