Re: fix iounmap and a pageattr memleak (x86 and x86-64)

Dave Hansen
2004-11-02T21:23:12Z

This patch:

> From: Andrea Arcangeli <andrea@novell.com>
>
> - fix silent memleak in the pageattr code that I found while searching
> for the bug Andi fixed in the second patch below (basically reference
> counting in split page was done on the pmd instead of the pte).
>
> - Part of this patch is also needed to make the above work on x86 (otherwise
> one of my new above BUGS() will trigger signalling the fact a bug was
> there). The below patch creates a subtle dependency that (_PAGE_PCD << 24)
> must not be zero. It's not the cleanest thing ever, but since it's an
> hardware bitflag I doubt it's going to break.
>
> Signed-off-by: Andi Kleen <ak@suse.de>
> Signed-off-by: Andrea Arcangeli <andrea@novell.com>
> Signed-off-by: Andrew Morton <akpm@osdl.org>
> ---
>
> 25-akpm/arch/i386/mm/ioremap.c | 4 ++--
> 25-akpm/arch/i386/mm/pageattr.c | 13 +++++++------
> 25-akpm/arch/x86_64/mm/ioremap.c | 14 +++++++-------
> 25-akpm/arch/x86_64/mm/pageattr.c | 23 ++++++++++++++---------
> 4 files changed, 30 insertions(+), 24 deletions(-)

is hitting this BUG() during bootup:

/* memleak and potential failed 2M page regeneration */
BUG_ON(!page_count(kpte_page));

in 2.6.10-rc1-mm2.

Dentry cache hash table entries: 131072 (order: 7, 524288 bytes)
Inode-cache hash table entries: 65536 (order: 6, 262144 bytes)
Memory: 511144k/524288k available (1856k kernel code, 12608k reserved,
1186k data, 164k init, 0k highmem)
Checking if this processor honours the WP bit even in supervisor mode... Ok.
Mount-cache hash table entries: 512 (order: 0, 4096 bytes)
------------[ cut here ]------------
kernel BUG at arch/i386/mm/pageattr.c:136!
invalid operand: 0000 [#1]
SMP DEBUG_PAGEALLOC
Modules linked in:
CPU: 0
EIP: 0060:[<c0113f48>] Not tainted VLI
EFLAGS: 00010046 (2.6.10-rc1-mm2)
EIP is at __change_page_attr+0x28c/0x358
eax: ffffffff ebx: 017ff163 ecx: 00000000 edx: c10001e0
esi: 00000000 edi: c000fff8 ebp: c10001e0 esp: c03f9d98
ds: 007b es: 007b ss: 0068
Process swapper (pid: 0, threadinfo=c03f9000 task=c0345b40)
Stack: c102ffe0 00000000 00000000 00000046 c0113ceb c17f9000 c102ff20
c102ff20 017ff163 00000000 017ff163 00000000 c0113ceb c17fe000
c102ffc0 c102ffc0 c1000000 c17ff000 c000fff8 017ff163 00000000
017ff163 00000000 00000000
Call Trace:
[<c0113ceb>] __change_page_attr+0x2f/0x358
[<c0113ceb>] __change_page_attr+0x2f/0x358
[<c011404a>] change_page_attr+0x36/0x54
[<c0114148>] kernel_map_pages+0x30/0x5f
[<c0137d80>] __alloc_pages+0x340/0x350
[<c0137dad>] __get_free_pages+0x1d/0x30
[<c013adfa>] kmem_getpages+0x26/0xd4
[<c013c221>] cache_grow+0xb1/0x150
[<c013c84a>] cache_alloc_refill+0x232/0x280
[<c013ccbe>] kmem_cache_alloc+0x5a/0x78
[<c01d4970>] idr_pre_get+0x1c/0x44
[<c0181b60>] sysfs_fill_super+0x0/0xa4
[<c01572cc>] set_anon_super+0x10/0xb8
[<c0156cff>] sget+0xb3/0x148
[<c0181b60>] sysfs_fill_super+0x0/0xa4
[<c0157636>] get_sb_single+0x26/0x8c
[<c0157608>] compare_single+0x0/0x8
[<c01572bc>] set_anon_super+0x0/0xb8
[<c0181c1d>] sysfs_get_sb+0x19/0x1d
[<c0181b60>] sysfs_fill_super+0x0/0xa4
[<c01576ea>] do_kern_mount+0x4e/0xd0
[<c015777d>] kern_mount+0x11/0x15
[<c0409962>] sysfs_init+0x1e/0x50
[<c0409430>] mnt_init+0xb4/0xc0
[<c040917a>] vfs_caches_init+0x7e/0x94
[<c03fa831>] start_kernel+0x12d/0x150
Code: c7 0f 75 f5 f0 ff 4d 04 eb 08 0f 0b 85 00 88 c1 2d c0 8b 45 00 89
ea f6 c4 80 74 07 8b 55 0c 8d 74 26 00 8b 42 04 83 f8 ff 75 08 <0f> 0b
88 00 88 c1 2d c0 a1 ac 6c 34 c0 a8 08 0f 84 aa 00 00 00

I'm tracking down now to see exactly what's going on. This just a
regular, plain 4-way x86 box with 4GB of RAM. Removing that BUG_ON()
lets me boot just fine.

kpte: c000fff8
address: c17ff000
kpte_page: c10001e0
pgprot_val(prot): 00000163
pgprot_val(PAGE_KERNEL): 00000163
(pte_val(*kpte) & _PAGE_PSE): 00000000