Re: tty-related oops in latest kernel(s)?

From: Alexey Dobriyan
Date: Wed May 30 2007 - 14:03:40 EST

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On Wed, May 30, 2007 at 09:09:45AM -0700, Andrew Morton wrote:
> On Wed, 30 May 2007 19:01:09 +0300 (EEST) Tero Roponen <teanropo@xxxxxx> wrote:
>
> > On Wed, 30 May 2007, Andrew Morton wrote:
> >
> > > On Wed, 30 May 2007 15:02:49 +0300 (EEST) Tero Roponen <teanropo@xxxxxx> wrote:
> > >
> > > > On Wed, 30 May 2007, Pekka Enberg wrote:
> > > >
> > > > > On 5/30/07, Tero Roponen <teanropo@xxxxxx> 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
>
> Whoa. Impressed.
>
> > *** 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.
> >
>
> cc's added ;)
>
> Thanks.
>
> Tony, this is with SLUB enabled, which might be detecting a
> hitherto-undetected bug.
>
> Config is at http://userweb.kernel.org/~akpm/config-tero.txt

Two suspicious things for me:

1)

--- a/drivers/video/neofb.c
+++ b/drivers/video/neofb.c
@@ -1295,7 +1295,7 @@ static int neofb_setcolreg(u_int regno,
outb(blue >> 10, 0x3c9);
break;
case 16:
- ((u32 *) fb->pseudo_palette)[regno] =
+ ((u16 *) fb->pseudo_palette)[regno] =
((red & 0xf800)) | ((green & 0xfc00) >> 5) |
((blue & 0xf800) >> 11);
break;

2) palette in neofb_par is "u32 palette[16];" which is 4x16 = 64 bytes.
struct fb_info::pseudo_palette is assigned to it in neo_alloc_fb_info().
Yet, we check at the beginning of neofb_setcolreg() for color map
length which neofb advertises as 256 which seems too many.

printk()s showing "regno" at the beginning of neofb_setcolreg()
welcome.

Alexey, who only knows how to spell framebuffer and a bit.

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Next message: Satyam Sharma: "Re: [-mm] Move zlib compression library to common directory [TAKE TWO]"
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