On 10/6/19 6:17 PM, Linus Torvalds wrote:
On Sun, Oct 6, 2019 at 5:04 PM Guenter Roeck <linux@xxxxxxxxxxxx> 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
