On Wed, 30 May 2007, Andrew Morton wrote:
> On Wed, 30 May 2007 15:02:49 +0300 (EEST) Tero Roponen <[email protected]> wrote:
>
> > On Wed, 30 May 2007, Pekka Enberg wrote:
> >
> > > On 5/30/07, Tero Roponen <[email protected]> wrote:
> > > > Hmmm, I just found something interesting. In 2.6.21.3 the /sbin/init
> > > > gets corrupted when I watch the video!
> > > >
> > > > $ cp /sbin/init init.before
> > > > $ mplayer kiwi.flv
> > > > $ cp /sbin/init init.after
> > > >
> > > > The sha1sums are here:
> > > >
> > > > 52c8d643057619cbe137b8e69d4709ce3bdd832d init.after
> > > > 8efc7864a5b535a9e336fa82e9d7f112f3d956c1 init.before
> > > >
> > > > It seems that something corrupts memory somewhere...
> > >
> > > To debug this a bit further:
> > >
> > > $ od -a -t x1 -v init.after > init.after.dump
> > > $ od -a -t x1 -v init.before > init.before.dump
> > > $ diff -u init.before.dump init.after.dump | less
> > >
> > > -0011340 nul nul nul e9 f0 fe ff ff ff % < soh enq bs h 80
> > > - 00 00 00 e9 f0 fe ff ff ff 25 3c 01 05 08 68 80
> > > +0010000 y ack nul nul y ack nul nul y ack nul nul y ack nul nul
> > > + 79 06 00 00 79 06 00 00 79 06 00 00 79 06 00 00
> > > +0010020 y ack nul nul y ack nul nul y ack nul nul y ack nul nul
> > > + 79 06 00 00 79 06 00 00 79 06 00 00 79 06 00 00
> > > +0011340 y ack nul nul y ack nul nul ff % < soh enq bs h 80
> > > + 79 06 00 00 79 06 00 00 ff 25 3c 01 05 08 68 80
> > >
> > > The file at offset 0010000 - 0011348 is overwritten with the byte
> > > pattern 79 06 00 00.
> > >
> > > Do you see anything in the logs or is this a silent corruption? Did
> > > you see this corruption with 2.6.19 or 2.6.22-rc3?
> > >
> >
> > I recompiled 2.6.22-rc3 and booted it with slub_debug. Now I can't oops
> > the kernel, but ./slab_info -v gives me a warning:
> >
> > neofb: no support for 32bpp
> > neofb: no support for 32bpp
> > neofb: no support for 32bpp
> > neofb: no support for 32bpp
> > neofb: no support for 32bpp
> > neofb: no support for 32bpp
> > neofb: no support for 32bpp
> > neofb: no support for 32bpp
> > neofb: no support for 32bpp
> > neofb: no support for 32bpp
> > neofb: no support for 32bpp
> > neofb: no support for 32bpp
> > neofb: no support for 32bpp
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1024x768) larger than the LCD panel (800x600)
> > Mode (1152x864) larger than the LCD panel (800x600)
> > Mode (1152x864) larger than the LCD panel (800x600)
> > Mode (1152x864) larger than the LCD panel (800x600)
> > Mode (1152x864) larger than the LCD panel (800x600)
> > Mode (1152x864) larger than the LCD panel (800x600)
> > Mode (1152x864) larger than the LCD panel (800x600)
> > Mode (1152x864) larger than the LCD panel (800x600)
> > Mode (1152x864) larger than the LCD panel (800x600)
> > Mode (1152x864) larger than the LCD panel (800x600)
> > Mode (1152x864) larger than the LCD panel (800x600)
> > Mode (1152x864) larger than the LCD panel (800x600)
> > Mode (1152x864) larger than the LCD panel (800x600)
> > Mode (1024x1024) larger than the LCD panel (800x600)
> > Mode (1024x1024) larger than the LCD panel (800x600)
> > Mode (1024x1024) larger than the LCD panel (800x600)
> > Mode (1024x1024) larger than the LCD panel (800x600)
> > Mode (1280x1024) larger than the LCD panel (800x600)
> > Mode (1280x1024) larger than the LCD panel (800x600)
> > Mode (1280x1024) larger than the LCD panel (800x600)
> > Mode (1280x1024) larger than the LCD panel (800x600)
> > *** SLUB kmalloc-1024: Redzone Active@0xc10be860 slab 0xc10217c0
> > offset=2144 flags=0x80004082 inuse=7 freelist=0x00000000
> > Bytes b4 0xc10be850: 00 00 00 00 00 00 00 00 5a 5a 5a 5a 5a 5a 5a 5a ........ZZZZZZZZ
> > Object 0xc10be860: 00 00 00 00 00 20 00 00 20 03 00 00 58 02 00 00 ............X...
> > Object 0xc10be870: 20 03 00 00 58 02 00 00 00 00 00 00 00 00 00 00 ....X...........
> > Object 0xc10be880: 10 00 00 00 00 00 00 00 0b 00 00 00 05 00 00 00 ................
> > Object 0xc10be890: 00 00 00 00 05 00 00 00 06 00 00 00 00 00 00 00 ................
> > Object 0xc10be8a0: 00 00 00 00 05 00 00 00 00 00 00 00 00 00 00 00 ................
> > Object 0xc10be8b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
> > Object 0xc10be8c0: ff ff ff ff ff ff ff ff 00 00 00 00 a8 61 00 00 ÿÿÿÿÿÿÿÿ....¨a..
> > Object 0xc10be8d0: 58 00 00 00 28 00 00 00 17 00 00 00 01 00 00 00 X...(...........
> > Redzone 0xc10bec60: 4d 6b 00 00 Mk..
> > FreePointer 0xc10bec64 -> 0x00006b4d
> > Last alloc: 0x6b4d jiffies_ago=4294923792 cpu=27469 pid=27469
> > Last free : 0x6b4d jiffies_ago=4294923792 cpu=27469 pid=27469
> > Filler 0xc10bec88: 4d 6b 00 00 4d 6b 00 00 Mk..Mk..
> > [<c013f717>] check_object+0x64/0x23d
> > [<c0141371>] validate_slab+0xff/0x12a
> > [<c01413aa>] validate_slab_slab+0xe/0x51
> > [<c0141488>] validate_store+0x9b/0xe8
> > [<c01343d1>] __handle_mm_fault+0x370/0x68b
> > [<c01413ed>] validate_store+0x0/0xe8
> > [<c013eaa6>] slab_attr_store+0x1e/0x22
> > [<c016e470>] sysfs_write_file+0xad/0xd6
> > [<c016e3c3>] sysfs_write_file+0x0/0xd6
> > [<c0143341>] vfs_write+0x8a/0x10c
> > [<c01437d7>] sys_write+0x41/0x67
> > [<c01022c2>] sysenter_past_esp+0x5f/0x85
> > =======================
> > @@@ SLUB kmalloc-1024: Restoring redzone (0xcc) from 0xc10bec60-0xc10bec63
> >
>
> So something did an overwrite of a 1024-byte kmalloc. Unfortunately that
> overwrite seems to have trashed our last-alloc info, so we don't know who
> allocated that memory. Darn.
>
> Does the problem go away if you disable CONFIG_SLUB and enable CONFIG_SLAB?
>
>
Hi,
after some trial and error I found a simple way to trigger the
corruption:
[root@terrop ~]# ./slabinfo -v
[root@terrop ~]# ./oops
[root@terrop ~]# ./slabinfo -v
*** SLUB kmalloc-1024: Redzone Active@0xc10be860 slab 0xc10217c0
offset=2144 flags=0x80004082 inuse=7 freelist=0x00000000
Bytes b4 0xc10be850: 00 00 00 00 00 00 00 00 5a 5a 5a 5a 5a 5a 5a 5a ........ZZZZZZZZ
Object 0xc10be860: 00 00 00 00 00 20 00 00 20 03 00 00 58 02 00 00 ............X...
Object 0xc10be870: 20 03 00 00 58 02 00 00 00 00 00 00 00 00 00 00 ....X...........
Object 0xc10be880: 18 00 00 00 00 00 00 00 10 00 00 00 08 00 00 00 ................
Object 0xc10be890: 00 00 00 00 08 00 00 00 08 00 00 00 00 00 00 00 ................
Object 0xc10be8a0: 00 00 00 00 08 00 00 00 00 00 00 00 00 00 00 00 ................
Object 0xc10be8b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
Object 0xc10be8c0: ff ff ff ff ff ff ff ff 00 00 00 00 a8 61 00 00 ÿÿÿÿÿÿÿÿ....¨a..
Object 0xc10be8d0: 58 00 00 00 28 00 00 00 17 00 00 00 01 00 00 00 X...(...........
Redzone 0xc10bec60: 6b 6b 6b 00 kkk.
FreePointer 0xc10bec64 -> 0x006b6b6b
Last alloc: 0x6b6b6b jiffies_ago=4287907122 cpu=7039851 pid=7039851
Last free : 0x6b6b6b jiffies_ago=4287907122 cpu=7039851 pid=7039851
Filler 0xc10bec88: 6b 6b 6b 00 6b 6b 6b 00 kkk.kkk.
[<c013f717>] check_object+0x64/0x23d
[<c0141371>] validate_slab+0xff/0x12a
[<c01413aa>] validate_slab_slab+0xe/0x51
[<c0141488>] validate_store+0x9b/0xe8
[<c01343d1>] __handle_mm_fault+0x370/0x68b
[<c01413ed>] validate_store+0x0/0xe8
[<c013eaa6>] slab_attr_store+0x1e/0x22
[<c016e470>] sysfs_write_file+0xad/0xd6
[<c016e3c3>] sysfs_write_file+0x0/0xd6
[<c0143341>] vfs_write+0x8a/0x10c
[<c01437d7>] sys_write+0x41/0x67
[<c01022c2>] sysenter_past_esp+0x5f/0x85
=======================
@@@ SLUB kmalloc-1024: Restoring redzone (0xcc) from 0xc10bec60-0xc10bec63
[root@terrop ~]# cat oops.c
#include <sys/ioctl.h>
#include <stdio.h>
#include <linux/fb.h>
#include <fcntl.h>
int main(void)
{
struct fb_var_screeninfo fbinfo;
int fd = open("/dev/fb0", O_RDWR);
if (fd < 0)
return 1;
/* Get screeninfo */
ioctl(fd, FBIOGET_VSCREENINFO, &fbinfo);
/* Change depth from current 16 to 24. */
fbinfo.bits_per_pixel = 24;
ioctl(fd, FBIOPUT_VSCREENINFO, &fbinfo);
return 0;
}
So this seems to be a framebuffer error.
--
Tero Roponen
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