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b3fd8e83ad
text_poke() can potentially compromise security as it sets temporary PTEs in the fixmap. These PTEs might be used to rewrite the kernel code from other cores accidentally or maliciously, if an attacker gains the ability to write onto kernel memory. Moreover, since remote TLBs are not flushed after the temporary PTEs are removed, the time-window in which the code is writable is not limited if the fixmap PTEs - maliciously or accidentally - are cached in the TLB. To address these potential security hazards, use a temporary mm for patching the code. Finally, text_poke() is also not conservative enough when mapping pages, as it always tries to map 2 pages, even when a single one is sufficient. So try to be more conservative, and do not map more than needed. Signed-off-by: Nadav Amit <namit@vmware.com> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Cc: <akpm@linux-foundation.org> Cc: <ard.biesheuvel@linaro.org> Cc: <deneen.t.dock@intel.com> Cc: <kernel-hardening@lists.openwall.com> Cc: <kristen@linux.intel.com> Cc: <linux_dti@icloud.com> Cc: <will.deacon@arm.com> Cc: Andy Lutomirski <luto@kernel.org> Cc: Borislav Petkov <bp@alien8.de> Cc: Dave Hansen <dave.hansen@intel.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Kees Cook <keescook@chromium.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Masami Hiramatsu <mhiramat@kernel.org> Cc: Rik van Riel <riel@surriel.com> Cc: Thomas Gleixner <tglx@linutronix.de> Link: https://lkml.kernel.org/r/20190426001143.4983-8-namit@vmware.com Signed-off-by: Ingo Molnar <mingo@kernel.org> |
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