From: Colin Ian King colin.king@canonical.com
commit 7298e3b0a149c91323b3205d325e942c3b3b9ef6 upstream.
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
BUG: unable to handle kernel paging request at 00000000000020d8 #PF error: [normal kernel read fault] PGD 0 P4D 0 Oops: 0000 [#1] SMP PTI CPU: 1 PID: 11039 Comm: stress-ng-idle- Not tainted 5.0.0-5-generic #6-Ubuntu Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1ubuntu1 04/01/2014 RIP: 0010:page_idle_get_page+0xc8/0x1a0 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 RSP: 0018:ffffafd7c672fde8 EFLAGS: 00010202 RAX: 0000000000000005 RBX: ffffe36341fff700 RCX: 000000000000000f RDX: 0000000000000284 RSI: 0000000000000275 RDI: 0000000001fff700 RBP: ffffafd7c672fe00 R08: ffffa0bc34056410 R09: 0000000000000276 R10: ffffa0bc754e9b40 R11: ffffa0bc330f6400 R12: 0000000000002080 R13: ffffe36341fff700 R14: 0000000000080000 R15: ffffa0bc330f6400 FS: 00007f0ec1ea5740(0000) GS:ffffa0bc7db00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 00000000000020d8 CR3: 0000000077d68000 CR4: 00000000000006e0 Call Trace: page_idle_bitmap_write+0x8c/0x140 sysfs_kf_bin_write+0x5c/0x70 kernfs_fop_write+0x12e/0x1b0 __vfs_write+0x1b/0x40 vfs_write+0xab/0x1b0 ksys_write+0x55/0xc0 __x64_sys_write+0x1a/0x20 do_syscall_64+0x5a/0x110 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@canonical.com Reviewed-by: Andrew Morton akpm@linux-foundation.org Acked-by: Vladimir Davydov vdavydov.dev@gmail.com Cc: Michal Hocko mhocko@suse.com Cc: Mike Rapoport rppt@linux.vnet.ibm.com Cc: Mel Gorman mgorman@techsingularity.net Cc: Stephen Rothwell sfr@canb.auug.org.au Cc: Andrey Ryabinin aryabinin@virtuozzo.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- mm/page_idle.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)
--- a/mm/page_idle.c +++ b/mm/page_idle.c @@ -136,7 +136,7 @@ static ssize_t page_idle_bitmap_read(str
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(st
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;