Messages in this thread |  | | From | (Linus Torvalds) | Subject | Re: Security question: "Text file busy" overwriting executables but not shared libraries? | Date | Thu, 4 Oct 2001 05:38:12 +0000 (UTC) |
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In article <01100319203903.00728@localhost.localdomain>, Rob Landley <landley@trommello.org> wrote: > >I.E. it seems like they go out of their way to ALLOW writing to the libaries. > (I assume they KNOW the difference between MAP_DENYWRITE, MAP_COPY, and >MAP_PRIVATE...?)
Note that the kernel will refuse to honour MAP_DENYWRITE from user space, so I'm afraid that changing ld.so won't do a thing.
The reason the kernel refuses to honour it, is that MAP_DENYWRITE is an excellent DoS-vehicle - you just mmap("/etc/passwd") with MAP_DENYWRITE, and even root cannot write to it.. Vary nasty.
Which is why the kernel only allows it when the binary loader itself sets the flag, because security-conscious application writers are already aware of the "oh, a running binary may not be writable" issues.
So sorry..
Linus
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