On Mon, 2019-06-03 at 06:56:57 UTC, Daniel Axtens wrote: > While developing kasan for 64-bit book3s, I hit the following stack > over-read. > > It occurs because the hypercall to put characters onto the terminal > takes 2 longs (128 bits/16 bytes) of characters at a time, and so > hvc_put_chars would unconditionally copy 16 bytes from the argument > buffer, regardless of supplied length. However, udbg_hvc_putc can > call hvc_put_chars with a single-byte buffer, leading to the error. > > [ 0.001931] > ================================================================== > [150/819] > [ 0.001933] BUG: KASAN: stack-out-of-bounds in hvc_put_chars+0xdc/0x110 > [ 0.001934] Read of size 8 at addr c0000000023e7a90 by task swapper/0 > [ 0.001934] > [ 0.001935] CPU: 0 PID: 0 Comm: swapper Not tainted > 5.2.0-rc2-next-20190528-02824-g048a6ab4835b #113 > [ 0.001935] Call Trace: > [ 0.001936] [c0000000023e7790] [c000000001b4a450] dump_stack+0x104/0x154 > (unreliable) > [ 0.001937] [c0000000023e77f0] [c0000000006d3524] > print_address_description+0xa0/0x30c > [ 0.001938] [c0000000023e7880] [c0000000006d318c] > __kasan_report+0x20c/0x224 > [ 0.001939] [c0000000023e7950] [c0000000006d19d8] kasan_report+0x18/0x30 > [ 0.001940] [c0000000023e7970] [c0000000006d4854] > __asan_report_load8_noabort+0x24/0x40 > [ 0.001941] [c0000000023e7990] [c0000000001511ac] hvc_put_chars+0xdc/0x110 > [ 0.001942] [c0000000023e7a10] [c000000000f81cfc] > hvterm_raw_put_chars+0x9c/0x110 > [ 0.001943] [c0000000023e7a50] [c000000000f82634] udbg_hvc_putc+0x154/0x200 > [ 0.001944] [c0000000023e7b10] [c000000000049c90] udbg_write+0xf0/0x240 > [ 0.001945] [c0000000023e7b70] [c0000000002e5d88] > console_unlock+0x868/0xd30 > [ 0.001946] [c0000000023e7ca0] [c0000000002e6e00] > register_console+0x970/0xe90 > [ 0.001947] [c0000000023e7d80] [c000000001ff1928] > register_early_udbg_console+0xf8/0x114 > [ 0.001948] [c0000000023e7df0] [c000000001ff1174] setup_arch+0x108/0x790 > [ 0.001948] [c0000000023e7e90] [c000000001fe41c8] start_kernel+0x104/0x784 > [ 0.001949] [c0000000023e7f90] [c00000000000b368] > start_here_common+0x1c/0x534 > [ 0.001950] > [ 0.001950] > [ 0.001951] Memory state around the buggy address: > [ 0.001952] c0000000023e7980: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 > [ 0.001952] c0000000023e7a00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > f1 f1 > [ 0.001953] >c0000000023e7a80: f1 f1 01 f2 f2 f2 00 00 00 00 00 00 00 00 > 00 00 > [ 0.001953] ^ > [ 0.001954] c0000000023e7b00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 > [ 0.001954] c0000000023e7b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 > 00 00 > [ 0.001955] > ================================================================== > > Document that a 16-byte buffer is requred, and provide it in udbg. > > CC: Dmitry Vyukov <dvyu...@google.com> > Signed-off-by: Daniel Axtens <d...@axtens.net>
Applied to powerpc next, thanks. https://git.kernel.org/powerpc/c/934bda59f286d0221f1a3ebab7f5156a cheers
