• Rick Edgecombe's avatar
    mm/vmalloc: Avoid rare case of flushing TLB with weird arguments · 31e67340
    Rick Edgecombe authored
    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: default avatarRick Edgecombe <rick.p.edgecombe@intel.com>
    Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
    Cc: Andy Lutomirski <luto@kernel.org>
    Cc: Borislav Petkov <bp@alien8.de>
    Cc: Dave Hansen <dave.hansen@intel.com>
    Cc: David S. Miller <davem@davemloft.net>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Meelis Roos <mroos@linux.ee>
    Cc: Nadav Amit <namit@vmware.com>
    Cc: Peter Zijlstra <peterz@infradead.org>
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Cc: Thomas Gleixner <tglx@linutronix.de>
    Fixes: 868b104d ("mm/vmalloc: Add flag for freeing of special permsissions")
    Link: https://lkml.kernel.org/r/20190527211058.2729-3-rick.p.edgecombe@intel.comSigned-off-by: default avatarIngo Molnar <mingo@kernel.org>
    31e67340
vmalloc.c 87.1 KB