From 31e67340cc65edfd9dac5ef26f81de8414ce5906 Mon Sep 17 00:00:00 2001 From: Rick Edgecombe Date: Mon, 27 May 2019 14:10:58 -0700 Subject: mm/vmalloc: Avoid rare case of flushing TLB with weird arguments In a rare case, flush_tlb_kernel_range() could be called with a start higher than the end. In vm_remove_mappings(), in case page_address() returns 0 for all pages (for example they were all in highmem), _vm_unmap_aliases() will be called with start = ULONG_MAX, end = 0 and flush = 1. If at the same time, the vmalloc purge operation is triggered by something else while the current operation is between remove_vm_area() and _vm_unmap_aliases(), then the vm mapping just removed will be already purged. In this case the call of vm_unmap_aliases() may not find any other mappings to flush and so end up flushing start = ULONG_MAX, end = 0. So only set flush = true if we find something in the direct mapping that we need to flush, and this way this can't happen. Signed-off-by: Rick Edgecombe Signed-off-by: Peter Zijlstra (Intel) Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Dave Hansen Cc: David S. Miller Cc: Linus Torvalds Cc: Meelis Roos Cc: Nadav Amit Cc: Peter Zijlstra Cc: Andrew Morton Cc: Thomas Gleixner Fixes: 868b104d7379 ("mm/vmalloc: Add flag for freeing of special permsissions") Link: https://lkml.kernel.org/r/20190527211058.2729-3-rick.p.edgecombe@intel.com Signed-off-by: Ingo Molnar --- mm/vmalloc.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) (limited to 'mm') diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 93b2dca2aadb..4c9e150e5ad3 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2125,6 +2125,7 @@ static void vm_remove_mappings(struct vm_struct *area, int deallocate_pages) { unsigned long start = ULONG_MAX, end = 0; int flush_reset = area->flags & VM_FLUSH_RESET_PERMS; + int flush_dmap = 0; int i; /* @@ -2163,6 +2164,7 @@ static void vm_remove_mappings(struct vm_struct *area, int deallocate_pages) if (addr) { start = min(addr, start); end = max(addr + PAGE_SIZE, end); + flush_dmap = 1; } } @@ -2172,7 +2174,7 @@ static void vm_remove_mappings(struct vm_struct *area, int deallocate_pages) * reset the direct map permissions to the default. */ set_area_direct_map(area, set_direct_map_invalid_noflush); - _vm_unmap_aliases(start, end, 1); + _vm_unmap_aliases(start, end, flush_dmap); set_area_direct_map(area, set_direct_map_default_noflush); } -- cgit v1.2.3