Messages in this thread | | | Date | Wed, 11 Mar 2020 17:17:56 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH -next] x86/mm/pat: mark an intentional data race |
| |
+ Paul.
On Mon, Feb 10, 2020 at 09:10:16AM -0500, Qian Cai wrote: > cpa_4k_install could be accessed concurrently as noticed by KCSAN, > > read to 0xffffffffaa59a000 of 8 bytes by interrupt on cpu 7: > cpa_inc_4k_install arch/x86/mm/pat/set_memory.c:131 [inline] > __change_page_attr+0x10cf/0x1840 arch/x86/mm/pat/set_memory.c:1514 > __change_page_attr_set_clr+0xce/0x490 arch/x86/mm/pat/set_memory.c:1636 > __set_pages_np+0xc4/0xf0 arch/x86/mm/pat/set_memory.c:2148 > __kernel_map_pages+0xb0/0xc8 arch/x86/mm/pat/set_memory.c:2178 > kernel_map_pages include/linux/mm.h:2719 [inline] <snip> > > write to 0xffffffffaa59a000 of 8 bytes by task 1 on cpu 6: > cpa_inc_4k_install arch/x86/mm/pat/set_memory.c:131 [inline] > __change_page_attr+0x10ea/0x1840 arch/x86/mm/pat/set_memory.c:1514 > __change_page_attr_set_clr+0xce/0x490 arch/x86/mm/pat/set_memory.c:1636 > __set_pages_p+0xc4/0xf0 arch/x86/mm/pat/set_memory.c:2129 > __kernel_map_pages+0x2e/0xc8 arch/x86/mm/pat/set_memory.c:2176 > kernel_map_pages include/linux/mm.h:2719 [inline] <snip> > > Both accesses are due to the same "cpa_4k_install++" in > cpa_inc_4k_install. A data race here could be potentially undesirable: > depending on compiler optimizations or how x86 executes a non-LOCK'd > increment, it may lose increments, corrupt the counter, etc. Since this > counter only seems to be used for printing some stats, this data race > itself is unlikely to cause harm to the system though. Thus, mark this > intentional data race using the data_race() marco. > > Suggested-by: Macro Elver <elver@google.com> > Signed-off-by: Qian Cai <cai@lca.pw> > --- > arch/x86/mm/pat/set_memory.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/arch/x86/mm/pat/set_memory.c b/arch/x86/mm/pat/set_memory.c > index c4aedd00c1ba..ea0b6df950ee 100644 > --- a/arch/x86/mm/pat/set_memory.c > +++ b/arch/x86/mm/pat/set_memory.c > @@ -128,7 +128,7 @@ static inline void cpa_inc_2m_checked(void) > > static inline void cpa_inc_4k_install(void) > { > - cpa_4k_install++; > + data_race(cpa_4k_install++); > } > > static inline void cpa_inc_lp_sameprot(int level) > --
Acked-by: Borislav Petkov <bp@suse.de>
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
| |