On Mon, Mar 25, 2002 at 11:00:47PM -0500, Benjamin LaHaise wrote:

Hello all,

The patch below fixes a problem whereby a vma which has its vm_start 
address changed by the file's mmap operation can result in the vma 
being inserted into the wrong location within the vma tree.  This 
results in page faults not being handled correctly leading to SEGVs, 
as well as various BUG()s hitting on exit of the mm.  The fix is to 
recalculate the insertion point when we know the address has changed.  
Comments?  Patch is against 2.4.19-pre4.

The patch is obviously safe.

However if the patch is needed it means the ->mmap also must do the
do_munmap stuff by hand internally, which is very ugly given we also did
our own do_munmap in a completly different region (the one requested by
the user). Our do_munmap should not happen if we place the mapping
elsewhere. If possible I would prefer to change those drivers to
advertise their enforced vm_start with a proper callback, the current
way is halfway broken still. BTW, which are those drivers, and why they
needs to enforce a certain vm_start (also despite MAP_FIXED that they
cannot check within the ->mmap callback)?

Andrea
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