On Wed, Aug 17, 2016 at 5:13 AM, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > Hi Kees, Al, > > Saw this when using NFS root on r8a7791/koelsch, using a tree based on > renesas-drivers-2016-08-16-v4.8-rc2: > > usercopy: kernel memory exposure attempt detected from c01ff000 > (<kernel text>) (4096 bytes) Hmmm, the kernel text exposure on ARM usually means the hardened usercopy patchset was applied to an ARM tree without the _etext patch: http://git.kernel.org/linus/14c4a533e0996f95a0a64dfd0b6252d788cebc74 If you _do_ have this patch already (and based on the comment below, I suspect you do: usually the missing _etext makes the system entirely unbootable), then we need to dig further. > ------------[ cut here ]------------ > kernel BUG at mm/usercopy.c:75! > Internal error: Oops - BUG: 0 [#1] SMP ARM > Modules linked in: > CPU: 1 PID: 1636 Comm: exim4 Not tainted > 4.8.0-rc2-koelsch-00407-g7a4ab698caefa57a-dirty #2901 > Hardware name: Generic R8A7791 (Flattened Device Tree) > task: eeae7100 task.stack: eeace000 > PC is at __check_object_size+0x2d0/0x390 > LR is at __check_object_size+0x2d0/0x390 > pc : [<c02d33fc>] lr : [<c02d33fc>] psr: 600f0013 > sp : eeacfe28 ip : 00000000 fp : c0200000 > r10: b6f9c000 r9 : eeacff0c r8 : 00000001 > r7 : c0e05444 r6 : c01fffff r5 : 00001000 r4 : c01ff000 > r3 : 00000001 r2 : 2ed71000 r1 : ef9b43f0 r0 : 0000005c > Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment user > Control: 30c5387d Table: 6dcd62c0 DAC: 55555555 > Process exim4 (pid: 1636, stack limit = 0xeeace210) > Stack: (0xeeacfe28 to 0xeead0000) > fe20: c095c004 00001000 00000002 ef9fcc80 eeacfe38 00001000 > fe40: c01ff000 00001000 00000000 eeacff14 eeacff0c b6f9c000 ef22d4ac c03eea60 > fe60: 00000001 00000000 00000000 ee78bf00 eeacff28 ef9fcfe0 00001000 c029c914 > fe80: 00000004 00000001 00000000 eeacff14 00000000 ef22d3b8 00001000 00000000 > fea0: ee78bf88 00000002 ef22d3b8 c06afb3c 00000000 c038a9c8 c0c4b780 c02a0cd8 > fec0: effce060 eeacff28 ef22d3b8 00000000 eeacff14 c0206ce4 eeace000 00000000 > fee0: 00000000 c0387698 c0387644 00000000 ee78bf00 eeacff88 00001000 c02d5550 > ff00: 00001000 c06afb3c 00000001 b6f9c000 00001000 00000000 00000000 00001000 > ff20: eeacff0c 00000001 ee78bf00 00000000 00001000 00000000 00000000 00000000 > ff40: 00000000 00000000 ef365e38 00001000 ee78bf00 b6f9c000 eeacff88 c02d6080 > ff60: ee78bf00 b6f9c000 00001000 ee78bf00 ee78bf00 00001000 b6f9c000 c0206ce4 > ff80: eeace000 c02d6cd8 00001000 00000000 00001000 7f723250 b6c2bbfc 00003fdf > ffa0: 00000003 c0206b40 7f723250 b6c2bbfc 00000004 b6f9c000 00001000 00000000 > ffc0: 7f723250 b6c2bbfc 00003fdf 00000003 7f71efdf 0000000a 7f71efc0 00000000 > ffe0: 00000000 be80f4ac b6b90817 b6bcadd6 400f0030 00000004 30133e52 60547340 > [<c02d33fc>] (__check_object_size) from [<c03eea60>] > (copy_page_to_iter+0x114/0x1f0) > [<c03eea60>] (copy_page_to_iter) from [<c029c914>] > (generic_file_read_iter+0x3a0/0x7e8) > [<c029c914>] (generic_file_read_iter) from [<c0387698>] > (nfs_file_read+0x54/0x98) > [<c0387698>] (nfs_file_read) from [<c02d5550>] (__vfs_read+0xdc/0x104) > [<c02d5550>] (__vfs_read) from [<c02d6080>] (vfs_read+0x94/0x100) > [<c02d6080>] (vfs_read) from [<c02d6cd8>] (SyS_read+0x40/0x80) > [<c02d6cd8>] (SyS_read) from [<c0206b40>] (ret_fast_syscall+0x0/0x34) > Code: e88d0021 e1a03004 e59f00b0 ebff176b (e7f001f2) > > Despite the BUG(), the system continues working. I assume exim4 got killed, though? If you can figure out what bytes are present at c01ff000, that may give us a clue. -Kees > > Gr{oetje,eeting}s, > > Geert > > -- > Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx > > In personal conversations with technical people, I call myself a hacker. But > when I'm talking to journalists I just say "programmer" or something like that. > -- Linus Torvalds -- Kees Cook Nexus Security -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>