From: Tianyu Lan <[email protected]> [ Upstream commit 4030b4c585c41eeefec7bd20ce3d0e100a0f2e4d ]
When the 'start' parameter is >= 0xFF000000 on 32-bit systems, or >= 0xFFFFFFFF'FF000000 on 64-bit systems, fill_gva_list() gets into an infinite loop. With such inputs, 'cur' overflows after adding HV_TLB_FLUSH_UNIT and always compares as less than end. Memory is filled with guest virtual addresses until the system crashes. Fix this by never incrementing 'cur' to be larger than 'end'. Reported-by: Jong Hyun Park <[email protected]> Signed-off-by: Tianyu Lan <[email protected]> Reviewed-by: Michael Kelley <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Peter Zijlstra <[email protected]> Cc: Thomas Gleixner <[email protected]> Fixes: 2ffd9e33ce4a ("x86/hyper-v: Use hypercall for remote TLB flush") Signed-off-by: Ingo Molnar <[email protected]> Signed-off-by: Sasha Levin <[email protected]> --- arch/x86/hyperv/mmu.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/arch/x86/hyperv/mmu.c b/arch/x86/hyperv/mmu.c index 56c9ebac946fe..47718fff0b797 100644 --- a/arch/x86/hyperv/mmu.c +++ b/arch/x86/hyperv/mmu.c @@ -57,12 +57,14 @@ static inline int fill_gva_list(u64 gva_list[], int offset, * Lower 12 bits encode the number of additional * pages to flush (in addition to the 'cur' page). */ - if (diff >= HV_TLB_FLUSH_UNIT) + if (diff >= HV_TLB_FLUSH_UNIT) { gva_list[gva_n] |= ~PAGE_MASK; - else if (diff) + cur += HV_TLB_FLUSH_UNIT; + } else if (diff) { gva_list[gva_n] |= (diff - 1) >> PAGE_SHIFT; + cur = end; + } - cur += HV_TLB_FLUSH_UNIT; gva_n++; } while (cur < end); -- 2.20.1
