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    proc: clean up and fix /proc/<pid>/mem handling · e268337d
    Linus Torvalds 提交于
    Jüri Aedla reported that the /proc/<pid>/mem handling really isn't very
    robust, and it also doesn't match the permission checking of any of the
    other related files.
    
    This changes it to do the permission checks at open time, and instead of
    tracking the process, it tracks the VM at the time of the open.  That
    simplifies the code a lot, but does mean that if you hold the file
    descriptor open over an execve(), you'll continue to read from the _old_
    VM.
    
    That is different from our previous behavior, but much simpler.  If
    somebody actually finds a load where this matters, we'll need to revert
    this commit.
    
    I suspect that nobody will ever notice - because the process mapping
    addresses will also have changed as part of the execve.  So you cannot
    actually usefully access the fd across a VM change simply because all
    the offsets for IO would have changed too.
    Reported-by: NJüri Aedla <asd@ut.ee>
    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
    e268337d
base.c 86.2 KB