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Message-ID: <c3e9ec03-5eb5-75bb-98da-63eaa9246cff@roeck-us.net>
Date: Sun, 6 Oct 2019 19:30:16 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Alexander Viro <viro@...iv.linux.org.uk>,
linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH] Convert filldir[64]() from __put_user() to
unsafe_put_user()
On 10/6/19 6:17 PM, Linus Torvalds wrote:
> On Sun, Oct 6, 2019 at 5:04 PM Guenter Roeck <linux@...ck-us.net> wrote:
[ ... ]
> And yes, I'll fix that name copy loop in filldir to align the
> destination first, *but* if I'm right, it means that something like
> this should also likely cause issues:
>
> #define _GNU_SOURCE
> #include <unistd.h>
> #include <sys/mman.h>
>
> int main(int argc, char **argv)
> {
> void *mymap;
> uid_t *bad_ptr = (void *) 0x01;
>
> /* Create unpopulated memory area */
> mymap = mmap(NULL, 16384, PROT_READ | PROT_WRITE, MAP_PRIVATE
> | MAP_ANONYMOUS, -1, 0);
>
> /* Unaligned uidpointer in that memory area */
> bad_ptr = mymap+1;
>
> /* Make the kernel do put_user() on it */
> return getresuid(bad_ptr, bad_ptr+1, bad_ptr+2);
> }
>
> because that simple user mode program should cause that same "page
> fault on unaligned put_user()" behavior as far as I can tell.
>
> Mind humoring me and trying that on your alpha machine (or emulator,
> or whatever)?
>
Here you are. This is with v5.4-rc2 and your previous patch applied
on top.
/ # ./mmtest
Unable to handle kernel paging request at virtual address 0000000000000004
mmtest(75): Oops -1
pc = [<0000000000000004>] ra = [<fffffc0000311584>] ps = 0000 Not tainted
pc is at 0x4
ra is at entSys+0xa4/0xc0
v0 = fffffffffffffff2 t0 = 0000000000000000 t1 = 0000000000000000
t2 = 0000000000000000 t3 = 0000000000000000 t4 = 0000000000000000
t5 = 000000000000fffe t6 = 0000000000000000 t7 = fffffc0007edc000
s0 = 0000000000000000 s1 = 00000001200006f0 s2 = 00000001200df19f
s3 = 00000001200ea0b9 s4 = 0000000120114630 s5 = 00000001201145d8
s6 = 000000011f955c50
a0 = 000002000002c001 a1 = 000002000002c005 a2 = 000002000002c009
a3 = 0000000000000000 a4 = ffffffffffffffff a5 = 0000000000000000
t8 = 0000000000000000 t9 = fffffc0000000000 t10= 0000000000000000
t11= 000000011f955788 pv = fffffc0000349450 at = 00000000f8db54d3
gp = fffffc0000f2a160 sp = 00000000ab237c72
Disabling lock debugging due to kernel taint
Trace:
Code:
00000000
00063301
000007b6
00001111
00003f8d
Segmentation fault
Guenter
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