On Tue, May 07, 2019 at 09:31:10AM -0700, Alexander Duyck wrote:
On Mon, May 6, 2019 at 10:40 PM Sasha Levin <sashal@xxxxxxxxxx> wrote:From: Mikhail Zaslonko <zaslonko@xxxxxxxxxxxxx> [ Upstream commit 2830bf6f05fb3e05bc4743274b806c821807a684 ] If memory end is not aligned with the sparse memory section boundary, the mapping of such a section is only partly initialized. This may lead to VM_BUG_ON due to uninitialized struct page access from is_mem_section_removable() or test_pages_in_a_zone() function triggered by memory_hotplug sysfs handlers: Here are the the panic examples: CONFIG_DEBUG_VM=y CONFIG_DEBUG_VM_PGFLAGS=y kernel parameter mem=2050M -------------------------- page:000003d082008000 is uninitialized and poisoned page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) Call Trace: ( test_pages_in_a_zone+0xde/0x160) show_valid_zones+0x5c/0x190 dev_attr_show+0x34/0x70 sysfs_kf_seq_show+0xc8/0x148 seq_read+0x204/0x480 __vfs_read+0x32/0x178 vfs_read+0x82/0x138 ksys_read+0x5a/0xb0 system_call+0xdc/0x2d8 Last Breaking-Event-Address: test_pages_in_a_zone+0xde/0x160 Kernel panic - not syncing: Fatal exception: panic_on_oops kernel parameter mem=3075M -------------------------- page:000003d08300c000 is uninitialized and poisoned page dumped because: VM_BUG_ON_PAGE(PagePoisoned(p)) Call Trace: ( is_mem_section_removable+0xb4/0x190) show_mem_removable+0x9a/0xd8 dev_attr_show+0x34/0x70 sysfs_kf_seq_show+0xc8/0x148 seq_read+0x204/0x480 __vfs_read+0x32/0x178 vfs_read+0x82/0x138 ksys_read+0x5a/0xb0 system_call+0xdc/0x2d8 Last Breaking-Event-Address: is_mem_section_removable+0xb4/0x190 Kernel panic - not syncing: Fatal exception: panic_on_oops Fix the problem by initializing the last memory section of each zone in memmap_init_zone() till the very end, even if it goes beyond the zone end. Michal said: : This has alwways been problem AFAIU. It just went unnoticed because we : have zeroed memmaps during allocation before f7f99100d8d9 ("mm: stop : zeroing memory during allocation in vmemmap") and so the above test : would simply skip these ranges as belonging to zone 0 or provided a : garbage. : : So I guess we do care for post f7f99100d8d9 kernels mostly and : therefore Fixes: f7f99100d8d9 ("mm: stop zeroing memory during : allocation in vmemmap") Link: http://lkml.kernel.org/r/20181212172712.34019-2-zaslonko@xxxxxxxxxxxxx Fixes: f7f99100d8d9 ("mm: stop zeroing memory during allocation in vmemmap") Signed-off-by: Mikhail Zaslonko <zaslonko@xxxxxxxxxxxxx> Reviewed-by: Gerald Schaefer <gerald.schaefer@xxxxxxxxxx> Suggested-by: Michal Hocko <mhocko@xxxxxxxxxx> Acked-by: Michal Hocko <mhocko@xxxxxxxx> Reported-by: Mikhail Gavrilov <mikhail.v.gavrilov@xxxxxxxxx> Tested-by: Mikhail Gavrilov <mikhail.v.gavrilov@xxxxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxx> Cc: Alexander Duyck <alexander.h.duyck@xxxxxxxxxxxxxxx> Cc: Pasha Tatashin <Pavel.Tatashin@xxxxxxxxxxxxx> Cc: Martin Schwidefsky <schwidefsky@xxxxxxxxxx> Cc: Heiko Carstens <heiko.carstens@xxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxxxx> --- mm/page_alloc.c | 12 ++++++++++++ 1 file changed, 12 insertions(+)Wasn't this patch reverted in Linus's tree for causing a regression on some platforms? If so I'm not sure we should pull this in as a candidate for stable should we, or am I missing something?
I saw a follow-up patch that should be queued too, but I didn't see that this one got reverted. -- Thanks, Sasha
