Re: [PATCH 5.10.y] nubus: Partially revert proc_create_single_data() conversion

[Greg KH <gregkh@linuxfoundation.org>]

On Tue, Jul 04, 2023 at 11:09:21AM +1000, Finn Thain wrote:
> The conversion to proc_create_single_data() introduced a regression
> whereby reading a file in /proc/bus/nubus results in a seg fault:
> 
>     # grep -r . /proc/bus/nubus/e/
>     Data read fault at 0x00000020 in Super Data (pc=0x1074c2)
>     BAD KERNEL BUSERR
>     Oops: 00000000
>     Modules linked in:
>     PC: [<001074c2>] PDE_DATA+0xc/0x16
>     SR: 2010  SP: 38284958  a2: 01152370
>     d0: 00000001    d1: 01013000    d2: 01002790    d3: 00000000
>     d4: 00000001    d5: 0008ce2e    a0: 00000000    a1: 00222a40
>     Process grep (pid: 45, task=142f8727)
>     Frame format=B ssw=074d isc=2008 isb=4e5e daddr=00000020 dobuf=01199e70
>     baddr=001074c8 dibuf=ffffffff ver=f
>     Stack from 01199e48:
> 	    01199e70 00222a58 01002790 00000000 011a3000 01199eb0 015000c0 00000000
> 	    00000000 01199ec0 01199ec0 000d551a 011a3000 00000001 00000000 00018000
> 	    d003f000 00000003 00000001 0002800d 01052840 01199fa8 c01f8000 00000000
> 	    00000029 0b532b80 00000000 00000000 00000029 0b532b80 01199ee4 00103640
> 	    011198c0 d003f000 00018000 01199fa8 00000000 011198c0 00000000 01199f4c
> 	    000b3344 011198c0 d003f000 00018000 01199fa8 00000000 00018000 011198c0
>     Call Trace: [<00222a58>] nubus_proc_rsrc_show+0x18/0xa0
>      [<000d551a>] seq_read+0xc4/0x510
>      [<00018000>] fp_fcos+0x2/0x82
>      [<0002800d>] __sys_setreuid+0x115/0x1c6
>      [<00103640>] proc_reg_read+0x5c/0xb0
>      [<00018000>] fp_fcos+0x2/0x82
>      [<000b3344>] __vfs_read+0x2c/0x13c
>      [<00018000>] fp_fcos+0x2/0x82
>      [<00018000>] fp_fcos+0x2/0x82
>      [<000b8aa2>] sys_statx+0x60/0x7e
>      [<000b34b6>] vfs_read+0x62/0x12a
>      [<00018000>] fp_fcos+0x2/0x82
>      [<00018000>] fp_fcos+0x2/0x82
>      [<000b39c2>] ksys_read+0x48/0xbe
>      [<00018000>] fp_fcos+0x2/0x82
>      [<000b3a4e>] sys_read+0x16/0x1a
>      [<00018000>] fp_fcos+0x2/0x82
>      [<00002b84>] syscall+0x8/0xc
>      [<00018000>] fp_fcos+0x2/0x82
>      [<0000c016>] not_ext+0xa/0x18
>     Code: 4e5e 4e75 4e56 0000 206e 0008 2068 ffe8 <2068> 0020 2008 4e5e 4e75 4e56 0000 2f0b 206e 0008 2068 0004 2668 0020 206b ffe8
>     Disabling lock debugging due to kernel taint
> 
>     Segmentation fault
> 
> The proc_create_single_data() conversion does not work because
> single_open(file, nubus_proc_rsrc_show, PDE_DATA(inode)) is not
> equivalent to the original code.
> 
> Fixes: 3f3942aca6da ("proc: introduce proc_create_single{,_data}")
> Cc: Christoph Hellwig <hch@lst.de>
> Cc: stable@vger.kernel.org # 5.6+
> Signed-off-by: Finn Thain <fthain@linux-m68k.org>
> Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Link: https://lore.kernel.org/r/d4e2a586e793cc8d9442595684ab8a077c0fe726.1678783919.git.fthain@linux-m68k.org
> Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
> (cherry picked from commit 0e96647cff9224db564a1cee6efccb13dbe11ee2)
> Signed-off-by: Finn Thain <fthain@linux-m68k.org>
> ---
>  drivers/nubus/proc.c | 22 +++++++++++++++++-----
>  1 file changed, 17 insertions(+), 5 deletions(-)
> 

Now queued up, thanks.

greg k-h