[PATCH][SRU][X/B/C/D/E] mm/page_idle.c: fix oops because end_pfn is larger than max_pfn

[Kamal Mostafa]

Clean cherry-pick; stable patch; looks fine.

Acked-by: Kamal Mostafa <kamal at canonical.com>

 -Kamal

On Wed, Jun 19, 2019 at 02:30:32PM +0100, Colin King wrote:
> From: Colin Ian King <colin.king at canonical.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1833410
> 
> Currently the calcuation of end_pfn can round up the pfn number to more
> than the actual maximum number of pfns, causing an Oops.  Fix this by
> ensuring end_pfn is never more than max_pfn.
> 
> This can be easily triggered when on systems where the end_pfn gets
> rounded up to more than max_pfn using the idle-page stress-ng stress test:
> 
> sudo stress-ng --idle-page 0
> 
> [ 3812.222790] BUG: unable to handle kernel paging request at 00000000000020d8
> [ 3812.224341] #PF error: [normal kernel read fault]
> [ 3812.225144] PGD 0 P4D 0
> [ 3812.225626] Oops: 0000 [#1] SMP PTI
> [ 3812.226264] CPU: 1 PID: 11039 Comm: stress-ng-idle- Not tainted 5.0.0-5-generic #6-Ubuntu
> [ 3812.227643] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014
> [ 3812.229286] RIP: 0010:page_idle_get_page+0xc8/0x1a0
> [ 3812.230173] Code: 0f b1 0a 75 7d 48 8b 03 48 89 c2 48 c1 e8 33 83 e0 07 48 c1 ea 36 48 8d 0c 40 4c 8d 24 88 49 c1 e4 07 4c 03 24 d5 00 89 c3 be <49> 8b 44 24 58 48 8d b8 80 a1 02 00 e8 07 d5 77 00 48 8b 53 08 48
> [ 3812.234641] RSP: 0018:ffffafd7c672fde8 EFLAGS: 00010202
> [ 3812.235792] RAX: 0000000000000005 RBX: ffffe36341fff700 RCX: 000000000000000f
> [ 3812.237739] RDX: 0000000000000284 RSI: 0000000000000275 RDI: 0000000001fff700
> [ 3812.239225] RBP: ffffafd7c672fe00 R08: ffffa0bc34056410 R09: 0000000000000276
> [ 3812.241027] R10: ffffa0bc754e9b40 R11: ffffa0bc330f6400 R12: 0000000000002080
> [ 3812.242555] R13: ffffe36341fff700 R14: 0000000000080000 R15: ffffa0bc330f6400
> [ 3812.244073] FS: 00007f0ec1ea5740(0000) GS:ffffa0bc7db00000(0000) knlGS:0000000000000000
> [ 3812.245968] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> [ 3812.247162] CR2: 00000000000020d8 CR3: 0000000077d68000 CR4: 00000000000006e0
> [ 3812.249045] Call Trace:
> [ 3812.249625] page_idle_bitmap_write+0x8c/0x140
> [ 3812.250567] sysfs_kf_bin_write+0x5c/0x70
> [ 3812.251406] kernfs_fop_write+0x12e/0x1b0
> [ 3812.252282] __vfs_write+0x1b/0x40
> [ 3812.253002] vfs_write+0xab/0x1b0
> [ 3812.253941] ksys_write+0x55/0xc0
> [ 3812.254660] __x64_sys_write+0x1a/0x20
> [ 3812.255446] do_syscall_64+0x5a/0x110
> [ 3812.256254] entry_SYSCALL_64_after_hwframe+0x44/0xa9
> 
> Link: http://lkml.kernel.org/r/20190618124352.28307-1-colin.king@canonical.com
> Fixes: 33c3fc71c8cf ("mm: introduce idle page tracking")
> Signed-off-by: Colin Ian King <colin.king at canonical.com>
> (cherry picked from commit d96d6145d9796d5f1eac242538d45559e9a23404 linux-next)
> Reviewed-by: Andrew Morton <akpm at linux-foundation.org>
> Acked-by: Vladimir Davydov <vdavydov.dev at gmail.com>
> Cc: Michal Hocko <mhocko at suse.com>
> Cc: Mike Rapoport <rppt at linux.vnet.ibm.com>
> Cc: Mel Gorman <mgorman at techsingularity.net>
> Cc: Stephen Rothwell <sfr at canb.auug.org.au>
> Cc: Andrey Ryabinin <aryabinin at virtuozzo.com>
> Cc: <stable at vger.kernel.org>
> Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
> Signed-off-by: Stephen Rothwell <sfr at canb.auug.org.au>
> ---
>  mm/page_idle.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/page_idle.c b/mm/page_idle.c
> index 0b39ec0c945c..295512465065 100644
> --- a/mm/page_idle.c
> +++ b/mm/page_idle.c
> @@ -136,7 +136,7 @@ static ssize_t page_idle_bitmap_read(struct file *file, struct kobject *kobj,
>  
>  	end_pfn = pfn + count * BITS_PER_BYTE;
>  	if (end_pfn > max_pfn)
> -		end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS);
> +		end_pfn = max_pfn;
>  
>  	for (; pfn < end_pfn; pfn++) {
>  		bit = pfn % BITMAP_CHUNK_BITS;
> @@ -181,7 +181,7 @@ static ssize_t page_idle_bitmap_write(struct file *file, struct kobject *kobj,
>  
>  	end_pfn = pfn + count * BITS_PER_BYTE;
>  	if (end_pfn > max_pfn)
> -		end_pfn = ALIGN(max_pfn, BITMAP_CHUNK_BITS);
> +		end_pfn = max_pfn;
>  
>  	for (; pfn < end_pfn; pfn++) {
>  		bit = pfn % BITMAP_CHUNK_BITS;
> -- 
> 2.20.1
> 
> 
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