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-0700 (PDT) Date: Mon, 7 Aug 2023 16:32:41 +0100 From: Mark Rutland To: John Hsu =?utf-8?B?KOioseawuOe/sCk=?= Cc: "catalin.marinas@arm.com" , "linux-kernel@vger.kernel.org" , "linux-mediatek@lists.infradead.org" , Xiaobing Shi =?utf-8?B?KOWPsuWwj+WFtSk=?= , Chunhui Li =?utf-8?B?KOadjuaYpei+iSk=?= , "linux-mm@kvack.org" , Kuan-Ying Lee =?utf-8?B?KOadjuWGoOepjik=?= , Casper Li =?utf-8?B?KOadjuS4reamrik=?= , "linux-arm-kernel@lists.infradead.org" , Will Deacon , Robin Murphy Subject: Re: [BUG kernel-5.15] aarch64: __pi_strncmp() out-of-bound error Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Queue-Id: 8098CA001D X-Rspam-User: X-Stat-Signature: wgszswjsd9uar7xqcgezt9mraujahwg9 X-Rspamd-Server: rspam03 X-HE-Tag: 1691422367-66367 X-HE-Meta: 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 Q9W/opbG Cz3sQOWPpEvl8aDAF31hxJr/BdL5IS/+efOV9uZYSxel5oLUdU4FafMIyiPtOURpojD36WscAEjruWVoAogyVYQSZfknJjqAT9kRqUqyJifAH/lFPEK/53LfAwKQHkzEQ0s85cGDrroW2g2lTQwws/yCjjfNFjSZkCt5s4xHZSqti8VFcY5uRrkDSPDgbKY/jCRhaZ48xdJQuPQ1GzIH4A7zcZfrqnH3Y3t2/Djzaaoz7fK4VN/SXA0VWohsWP47eKwIPvHE3ilKZ7Ah7XnunrxdU+ZkVEMVcLm/Y X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Aug 07, 2023 at 12:31:45PM +0000, John Hsu (許永翰) wrote: > Hi ARM maintainers, > > We met this issue under our internal test. > It seems that __pi_strncmp() reads out-of-bound. > > [ 7445.268043][ T382] ueventd: [name:fault&]Unable to handle kernel > paging request at virtual address ffffff803fd3f000 > [ 7445.268078][ T382] ueventd: [name:fault&]Mem abort info: > [ 7445.268084][ T382] ueventd: [name:fault&] ESR = 0x96000007 > [ 7445.268089][ T382] ueventd: [name:fault&] EC = 0x25: DABT (current > EL), IL = 32 bits > [ 7445.268095][ T382] ueventd: [name:fault&] SET = 0, FnV = 0 > [ 7445.268100][ T382] ueventd: [name:fault&] EA = 0, S1PTW = 0 > [ 7445.268105][ T382] ueventd: [name:fault&] FSC = 0x07: level 3 > translation fault > [ 7445.268110][ T382] ueventd: [name:fault&]Data abort info: > [ 7445.268115][ T382] ueventd: [name:fault&] ISV = 0, ISS = > 0x00000007 > [ 7445.268120][ T382] ueventd: [name:fault&] CM = 0, WnR = 0 > [ 7445.268126][ T382] ueventd: [name:fault&]swapper pgtable: 4k pages, > 39-bit VAs, pgdp=00000000426c6000 > [ 7445.268133][ T382] ueventd: [name:fault&][ffffff803fd3f000] > pgd=1800000327ff5003, p4d=1800000327ff5003, pud=1800000327ff5003, > pmd=1800000327fef003, pte=0000000000000000 > [ 7445.268154][ T382] ueventd: [name:traps&]Internal error: Oops: > 96000007 [#1] PREEMPT SMP > [ 7445.268278][ T382] ueventd: [name:mrdump&]Kernel Offset: > 0x2825400000 from 0xffffffc008000000 > [ 7445.268286][ T382] ueventd: [name:mrdump&]PHYS_OFFSET: 0x40000000 > [ 7445.268294][ T382] ueventd: [name:mrdump&]pstate: 82400005 (Nzcv > daif +PAN -UAO) > [ 7445.268301][ T382] ueventd: [name:mrdump&]pc : [0xffffffe82d420210] > __pi_strncmp+0x1a0/0x1c4 > [ 7445.268310][ T382] ueventd: [name:mrdump&]lr : [0xffffffe82dbe12c0] > __security_genfs_sid+0x100/0x168 > [ 7445.268319][ T382] ueventd: [name:mrdump&]sp : ffffffc0097cb8b0 > … > [ 7445.269337][ T382] ueventd: CPU: 0 PID: 382 Comm: ueventd Tainted: > G S W OE 5.15.41-android13-8-gb1f1ad628628 #1 > [ 7445.269347][ T382] ueventd: Hardware name: MT6886(ENG) (DT) > [ 7445.269354][ T382] ueventd: Call trace: > [ 7445.269359][ T382] ueventd: dump_backtrace+0x0/0x2a8 > [ 7445.269374][ T382] ueventd: dump_stack_lvl+0x74/0xa4 > [ 7445.269384][ T382] ueventd: dump_stack+0x14/0x1c > [ 7445.269391][ T382] ueventd: mrdump_common_die+0x32c/0x5ac [mrdump] > [ 7445.269470][ T382] ueventd: ipanic_die+0x1c/0x28 [mrdump] > [ 7445.269539][ T382] ueventd: __die+0xbc/0x308 > [ 7445.269548][ T382] ueventd: die+0xd8/0x500 > [ 7445.269556][ T382] ueventd: die_kernel_fault+0x94/0xa8 > [ 7445.269565][ T382] ueventd: __do_kernel_fault+0x1d8/0x214 > [ 7445.269571][ T382] ueventd: do_bad_area+0x40/0x174 > [ 7445.269579][ T382] ueventd: do_translation_fault+0x48/0x54 > [ 7445.269585][ T382] ueventd: do_mem_abort+0x3c/0x100 > [ 7445.269592][ T382] ueventd: el1_abort+0x38/0x54 > [ 7445.269602][ T382] ueventd: el1h_64_sync_handler+0x54/0x88 > [ 7445.269610][ T382] ueventd: el1h_64_sync+0x78/0x7c > [ 7445.269618][ T382] ueventd: __pi_strncmp+0x1a0/0x1c4 > [ 7445.269626][ T382] ueventd: selinux_genfs_get_sid+0x114/0x220 > [ 7445.269636][ T382] ueventd: inode_doinit_with_dentry+0x3d0/0x598 > [ 7445.269644][ T382] ueventd: selinux_d_instantiate+0x1c/0x24 > [ 7445.269652][ T382] ueventd: d_splice_alias+0x5c/0x280 > [ 7445.269662][ T382] ueventd: kernfs_iop_lookup+0xec/0x21c > [ 7445.269674][ T382] ueventd: __lookup_slow+0xc4/0x150 > [ 7445.269684][ T382] ueventd: lookup_slow+0x40/0xf0 > [ 7445.269690][ T382] ueventd: walk_component+0x144/0x160 > [ 7445.269696][ T382] ueventd: link_path_walk+0x25c/0x344 > [ 7445.269703][ T382] ueventd: path_lookupat+0x64/0x120 > [ 7445.269710][ T382] ueventd: filename_lookup+0xc4/0x1b0 > [ 7445.269718][ T382] ueventd: user_path_at_empty+0x48/0xb4 > [ 7445.269725][ T382] ueventd: do_faccessat+0xa8/0x1f0 > [ 7445.269732][ T382] ueventd: __arm64_sys_faccessat+0x20/0x28 > [ 7445.269738][ T382] ueventd: invoke_syscall+0x3c/0xf0 > [ 7445.269746][ T382] ueventd: el0_svc_common+0x84/0xe8 > [ 7445.269753][ T382] ueventd: do_el0_svc+0x20/0x84 > [ 7445.269759][ T382] ueventd: el0_svc+0x1c/0x48 > [ 7445.269766][ T382] ueventd: el0t_64_sync_handler+0x7c/0xd8 > [ 7445.269773][ T382] ueventd: el0t_64_sync+0x15c/0x160 > > We found that we hit this issue when we compare these two strings. > > ________________address|_0__1__2__3__4__5__6__7__8__9__A__B__C__D__E__F > __ 0123456789ABCDEF > NSD:FFFFFF80089EDA00|>2F 64 65 76 69 63 65 73 2F 76 69 72 74 75 61 > 6C /devices/virtual > NSD:FFFFFF80089EDA10| 2F 62 6C 6F 63 6B 2F 00 E0 03 01 AA E1 03 02 > AA /block/......... > > ________________address|_0__1__2__3__4__5__6__7__8__9__A__B__C__D__E__F > __ 0123456789ABCDEF > NSD:FFFFFF803FD3EFE0| 00 00 00 00 00 00 00 00 00 00 2F 64 65 76 69 > 63 ........../devic > NSD:FFFFFF803FD3EFF0| 65 73>2F 76 69 72 74 75 61 6C 2F 6D 69 73 63 > 00 es/virtual/misc. > NSD:FFFFFF803FD3F000| ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? > ?? > NSD:FFFFFF803FD3F0E0| ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? ?? > ?? > > We observe the second string is put at the tail of the first page and > the next page is unreadable. > Thus, we made a simple test as below and it can reproduce this issue. > > static noinline void strncmp_ut(void) > { > int ret = 0; > int size = 4096; > char *src1 = vmalloc(size); > char *src2 = vmalloc(size); > char *str1 = "/devices/virtual/block/"; > char *str2 = "/devices/virtual/misc"; > int len1 = strlen(str1); > int len2 = strlen(str2); > char *str1_start, *str2_start; > > pr_info("src1: %px\n", src1); > pr_info("src2: %px\n", src2); > pr_info("len1 :%d, len2: %d\n", len1, len2); > > memset(src1, 0, size); > strncpy(&src1[size-len1-1], str1, len1); > memset(src2, 0, size); > strncpy(&src2[size-len2-1], str2, len2); > > str1_start = src1 + size - len1 - 1; > pr_info("str1_start: %px", str1_start); > str2_start = src2 + size - len2 - 1; > pr_info("str2_start: %px", str2_start); > ret = strncmp(str1_start, str2_start, len1); > pr_info("ret: %d\n", ret); > } > > > Does any issue exist in __pi_strncmp in kernel-5.15? There's no known issue, but the implementation change substantially in commit: 387d828adffcf1eb ("arm64: lib: Import latest version of Arm Optimized Routines' strncmp") ... which added additional alignment restrictions to accesses to avoid crossing an MTE tag granule. Using your test on v6.5-rc3 I could not trigger the issue, but I could trigger the issue atop v5.15: [ 1.639268] src1: ffff800010005000 [ 1.639982] src2: ffff80001000d000 [ 1.640758] len1 :23, len2: 21 [ 1.641098] str1_start: ffff800010005fe8 [ 1.641202] str2_start: ffff80001000dfea [ 1.642312] Unable to handle kernel paging request at virtual address ffff80001000e000 [ 1.643237] Mem abort info: [ 1.643858] ESR = 0x96000007 [ 1.644201] EC = 0x25: DABT (current EL), IL = 32 bits [ 1.644453] SET = 0, FnV = 0 [ 1.644979] EA = 0, S1PTW = 0 [ 1.645212] FSC = 0x07: level 3 translation fault [ 1.645492] Data abort info: [ 1.645638] ISV = 0, ISS = 0x00000007 [ 1.645818] CM = 0, WnR = 0 [ 1.646075] swapper pgtable: 4k pages, 48-bit VAs, pgdp=000000007a611000 [ 1.646417] [ffff80001000e000] pgd=100000004001d003, p4d=100000004001d003, pud=100000004001e003, pmd=100000004001f003, pte=0000000000000000 [ 1.648699] Internal error: Oops: 96000007 [#1] PREEMPT SMP [ 1.649681] Modules linked in: [ 1.650322] CPU: 0 PID: 1 Comm: swapper/0 Not tainted 5.15.0-dirty #1 [ 1.650994] pstate: 80400005 (Nzcv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--) [ 1.651475] pc : __pi_strncmp+0x1a0/0x1c4 [ 1.652860] lr : strncmp_ut+0xf4/0x118 [ 1.653133] sp : ffff80001009bdd0 [ 1.653680] x29: ffff80001009bdd0 x28: 0000000000000000 x27: 0000000000000000 [ 1.654134] x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000 [ 1.654453] x23: ffffa050aff25000 x22: 0000000000001000 x21: ffff800010005fe8 [ 1.654774] x20: ffff80001000dfea x19: ffff80001000dff7 x18: 0000000000000006 [ 1.655138] x17: 687469726f676c61 x16: 2046454420504d49 x15: ffff80001009b950 [ 1.655462] x14: 0000000000000008 x13: ffffffffffffffff x12: 00000000000002dc [ 1.656107] x11: 0101010101010101 x10: ffffa050afc9c540 x9 : 7f7f7f7f7f7f7f7f [ 1.656467] x8 : 6b6074737168752e x7 : ffffa050afc9ae60 x6 : 0000000000000000 [ 1.656769] x5 : 0000000000000000 x4 : 6c6175747269762f x3 : 2f6b636f6c622f6c [ 1.657083] x2 : 0000000000000007 x1 : ffff80001000dff2 x0 : ffff800010005ff0 [ 1.657576] Call trace: [ 1.657920] __pi_strncmp+0x1a0/0x1c4 [ 1.658179] smp_cpus_done+0xb4/0xc0 [ 1.658363] smp_init+0x80/0x90 [ 1.658516] kernel_init_freeable+0x12c/0x290 [ 1.658792] kernel_init+0x28/0x130 [ 1.658966] ret_from_fork+0x10/0x20 [ 1.659564] Code: b4fff762 d1002000 d1002021 f8626803 (f8626824) [ 1.661848] ---[ end trace 5ce515dccfbd3da3 ]--- [ 1.663291] Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b [ 1.663861] SMP: stopping secondary CPUs [ 1.667296] ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]--- That __pi_strncmp+0x1a0/0x1c4 is right at the end of __pi_strcmp(): | L(done_loop): | /* We found a difference or a NULL before the limit was reached. */ | and limit, limit, #7 | cbz limit, L(not_limit) | /* Read the last word. */ | sub src1, src1, 8 | sub src2, src2, 8 | ldr data1, [src1, limit] | ldr data2, [src2, limit] // <----------- Faulting LDR here | sub tmp1, data1, zeroones | orr tmp2, data1, #REP8_7f | eor diff, data1, data2 /* Non-zero if differences found. */ | bics has_nul, tmp1, tmp2 /* Non-zero if NUL terminator. */ | ccmp diff, #0, #0, eq | b.ne L(not_limit) | | L(ret0): | mov result, #0 | ret Thanks, Mark.