[syzbot] [riscv?] riscv/fixes boot error: kernel BUG in __phys_addr_symbol

[Alexandre Ghiti]

On 08/12/2023 18:18, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit:    eb46a0076501 riscv: Check if the code to patch lies in the..
> git tree:       git://git.kernel.org/pub/scm/linux/kernel/git/riscv/linux.git fixes
> console output: https://syzkaller.appspot.com/x/log.txt?x=14aa707ae80000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=a5c1ede998d7cef2
> dashboard link: https://syzkaller.appspot.com/bug?extid=afb726d49f84c8d95ee1
> compiler:       riscv64-linux-gnu-gcc (Debian 12.2.0-13) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
> userspace arch: riscv64
>
> Downloadable assets:
> disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/a741b348759c/non_bootable_disk-eb46a007.raw.xz
> vmlinux: https://storage.googleapis.com/syzbot-assets/472c8c5dc639/vmlinux-eb46a007.xz
> kernel image: https://storage.googleapis.com/syzbot-assets/21ee09184ba1/Image-eb46a007.xz
>
> IMPORTANT: if you fix the issue, please add the following tag to the commit:
> Reported-by: syzbot+afb726d49f84c8d95ee1 at syzkaller.appspotmail.com
>
> ------------[ cut here ]------------
> kernel BUG at arch/riscv/mm/physaddr.c:31!
> Kernel BUG [#1]
> Modules linked in:
> CPU: 0 PID: 1 Comm: swapper/0 Not tainted 6.7.0-rc1-syzkaller-geb46a0076501 #0
> Hardware name: riscv-virtio,qemu (DT)
> epc : __phys_addr_symbol+0x144/0x150 arch/riscv/mm/physaddr.c:31
>   ra : __phys_addr_symbol+0x144/0x150 arch/riscv/mm/physaddr.c:31
> epc : ffffffff800200b4 ra : ffffffff800200b4 sp : ff20000000013d10
>   gp : ffffffff861f60a0 tp : ff6000000b260000 t0 : 26747970652d3e69
>   t1 : fffffffef0a8ad5d t2 : 0000000000000000 s0 : ff20000000013d40
>   s1 : ff60000003a00000 a0 : 0000000000000006 a1 : ffffffff80000000
>   a2 : 0000000000000002 a3 : ffffffff800200b4 a4 : 0000000000000000
>   a5 : ff6000000b261000 a6 : 0000000000000003 a7 : ffffffff85456aef
>   s2 : ffffffff8816d000 s3 : ffffffff80000000 s4 : ffffffff84e6f2b0
>   s5 : ff60000003a00000 s6 : 0000000000000000 s7 : 0000000000000000
>   s8 : ffffffff861f5c40 s9 : 0000000000000000 s10: 0000000000000000
>   s11: 0000000000000000 t3 : ffffffffffffffff t4 : fffffffef0a8ad5d
>   t5 : fffffffef0a8ad5e t6 : ff60000013e80c70
> status: 0000000200000120 badaddr: 0000000000000000 cause: 0000000000000003
> [<ffffffff800200b4>] __phys_addr_symbol+0x144/0x150 arch/riscv/mm/physaddr.c:31
> [<ffffffff80019ede>] __set_memory+0x1c0/0x762 arch/riscv/mm/pageattr.c:308
> [<ffffffff8001a4a4>] set_memory_rw_nx+0x24/0x30 arch/riscv/mm/pageattr.c:346
> [<ffffffff80008778>] set_kernel_memory arch/riscv/include/asm/set_memory.h:27 [inline]
> [<ffffffff80008778>] free_initmem+0x52/0x8c arch/riscv/kernel/setup.c:323
> [<ffffffff837334e6>] kernel_init+0x44/0x21e init/main.c:1450
> [<ffffffff83745cb2>] ret_from_fork+0xe/0x1c arch/riscv/kernel/entry.S:221
> Code: 84b3 4124 b745 4985 1996 bf65 7097 0025 80e7 ecc0 (9002) 7097
> ---[ end trace 0000000000000000 ]---


Ok, that's for me, lm_alias() actually does not work for linear mapping 
addresses since it assumes that the address lies in the kernel mapping, 
my bad. I'll fix that either by "extending" lm_alias() to linear mapping 
addresses or directly in the riscv code, not sure right now what's the 
best solution.

Thanks for the report,

Alex


> ----------------
> Code disassembly (best guess):
>     0:	412484b3          	sub	s1,s1,s2
>     4:	b745                	j	0xffffffffffffffa4
>     6:	4985                	li	s3,1
>     8:	1996                	sll	s3,s3,0x25
>     a:	bf65                	j	0xffffffffffffffc2
>     c:	00257097          	auipc	ra,0x257
>    10:	ecc080e7          	jalr	-308(ra) # 0x256ed8
> * 14:	9002                	ebreak <-- trapping instruction
>    16:	97 70             	Address 0x16 is out of bounds.
>
>
> ---
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