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SubjectRe: general protection fault: 0000 [#1] SMP
On Mon, 22 Nov 2010, Justin P. Mattock wrote:

> <---- cut -------->
>
> cleaned the thread up.. Anyways after doing some debugging with gdb and with
> valgrind for an application that keeps segfaulting I noticed this in dmesg:
>
> [ 3028.571941] FIREWALL:INPUT IN=wlan0 OUT=
> MAC=ff:ff:ff:ff:ff:ff:00:23:12:65:cb:02:08:00 SRC=0.0.0.0
> DST=255.255.255.255 LEN=328 TOS=0x00 PREC=0x00 TTL=255 ID=57984 PROTO=UDP
> SPT=68 DPT=67 LEN=308
> [ 3061.177655] BUG: Bad page state in process make pfn:2134c
> [ 3061.177661] page:ffffea00007438a0 count:0 mapcount:0 mapping: (null)
> index:0x507
> [ 3061.177663] page flags: 0x4000000000000008(uptodate)
> [ 3061.177669] Pid: 5691, comm: make Not tainted 2.6.37-rc2-00039-g0211924
> #7
> [ 3061.177671] Call Trace:
> [ 3061.177680] [<ffffffff810c5900>] ? dump_page+0xc0/0xc5
> [ 3061.177684] [<ffffffff810c5f18>] bad_page+0xd8/0xea
> [ 3061.177688] [<ffffffff810c7aeb>] get_page_from_freelist+0x344/0x4a0
> [ 3061.177693] [<ffffffff811bf123>] ? inode_has_perm+0x68/0x6a
> [ 3061.177697] [<ffffffff810c7d6b>] __alloc_pages_nodemask+0x124/0x645
> [ 3061.177701] [<ffffffff810f7cf2>] ? __dentry_open+0x194/0x2a1
> [ 3061.177705] [<ffffffff810dc155>] handle_mm_fault+0x2a8/0x82f
> [ 3061.177710] [<ffffffff811056ec>] ? do_filp_open+0x1f3/0x646
> [ 3061.177714] [<ffffffff810f4226>] ? check_object+0x13b/0x1eb
> [ 3061.177719] [<ffffffff81447d8e>] do_page_fault+0x3ec/0x411
> [ 3061.177722] [<ffffffff810f4b95>] ? free_debug_processing+0x1c5/0x208
> [ 3061.177726] [<ffffffff81103958>] ? getname+0x2c/0x1be
> [ 3061.177728] [<ffffffff810f4d08>] ? __slab_free+0x130/0x145
> [ 3061.177732] [<ffffffff81444e25>] page_fault+0x25/0x30
> [ 3061.177734] Disabling lock debugging due to kernel taint
> [ 3126.418774] type=1400 audit(1290451825.417:178): avc: denied
>
> from what I remember using valgirnd with the app took a while to load but am
> unsure if is the reason for the above message.

This particular error is almost certainly fixed by rc3's patch below.
Whether your earlier errors are a side-effect of the same Uptodate bug
I cannot say: it's conceivable, but I don't see it as likely. Maybe
you should just move up to rc3 and see what happens with that.

Hugh

From: Markus Trippelsdorf <markus@trippelsdorf.de>
Date: Thu, 18 Nov 2010 02:46:06 +0000 (-0500)
Subject: ext4: fix setting random pages PageUptodate
X-Git-Tag: v2.6.37-rc3~1^2~5
X-Git-Url: http://127.0.0.1:1234/?p=.git;a=commitdiff_plain;h=08da1193d2c8c7a25d0cef7f85d0b9f1ad7c583a
ext4: fix setting random pages PageUptodate

ext4_end_bio calls put_page and kmem_cache_free before calling
SetPageUpdate(). This can result in setting the PageUptodate bit on
random pages and causes the following BUG:

BUG: Bad page state in process rm pfn:52e54
page:ffffea0001222260 count:0 mapcount:0 mapping: (null) index:0x0
arch kernel: page flags: 0x4000000000000008(uptodate)
Fix the problem by moving put_io_page() after the SetPageUpdate() call.

Thanks to Hugh Dickins for analyzing this problem.

Reported-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Tested-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: Markus Trippelsdorf <markus@trippelsdorf.de>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index 7f5451c..beacce1 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -237,8 +237,6 @@ static void ext4_end_bio(struct bio *bio, int error)
} while (bh != head);
}

- put_io_page(io_end->pages[i]);
-
/*
* If this is a partial write which happened to make
* all buffers uptodate then we can optimize away a
@@ -248,6 +246,8 @@ static void ext4_end_bio(struct bio *bio, int error)
*/
if (!partial_write)
SetPageUptodate(page);
+
+ put_io_page(io_end->pages[i]);
}
io_end->num_io_pages = 0;
inode = io_end->inode;

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