Messages in this thread | | | Date | Mon, 21 Apr 2003 22:28:53 +0200 | From | Manfred Spraul <> | Subject | [RFC, PATCH] fix verify_write for 80386 support |
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Real 80386 cpus have a special feature: they ignore the write-protected bit in the page tables if the kernel runs at ring 0. This feature breaks COW, the software must manually check the write protected bit before writing.
Right now the check happens only in access_ok(VERIFY_WRITE). This is broken, because: - some codepaths call access_ok(VERIFY_READ), and then write. - kswapd might change the page permissions between access_ok and the actual write access.
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