From 41e8149c8892ed1962bd15350b3c3e6e90cba7f4 Mon Sep 17 00:00:00 2001 From: Adrian Ratiu Date: Fri, 2 Aug 2024 11:02:25 +0300 Subject: proc: add config & param to block forcing mem writes This adds a Kconfig option and boot param to allow removing the FOLL_FORCE flag from /proc/pid/mem write calls because it can be abused. The traditional forcing behavior is kept as default because it can break GDB and some other use cases. Previously we tried a more sophisticated approach allowing distributions to fine-tune /proc/pid/mem behavior, however that got NAK-ed by Linus [1], who prefers this simpler approach with semantics also easier to understand for users. Link: https://lore.kernel.org/lkml/CAHk-=wiGWLChxYmUA5HrT5aopZrB7_2VTa0NLZcxORgkUe5tEQ@mail.gmail.com/ [1] Cc: Doug Anderson Cc: Jeff Xu Cc: Jann Horn Cc: Kees Cook Cc: Ard Biesheuvel Cc: Christian Brauner Suggested-by: Linus Torvalds Signed-off-by: Linus Torvalds Signed-off-by: Adrian Ratiu Link: https://lore.kernel.org/r/20240802080225.89408-1-adrian.ratiu@collabora.com Signed-off-by: Christian Brauner --- security/Kconfig | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) (limited to 'security') diff --git a/security/Kconfig b/security/Kconfig index 412e76f1575d..a93c1a9b7c28 100644 --- a/security/Kconfig +++ b/security/Kconfig @@ -19,6 +19,38 @@ config SECURITY_DMESG_RESTRICT If you are unsure how to answer this question, answer N. +choice + prompt "Allow /proc/pid/mem access override" + default PROC_MEM_ALWAYS_FORCE + help + Traditionally /proc/pid/mem allows users to override memory + permissions for users like ptrace, assuming they have ptrace + capability. + + This allows people to limit that - either never override, or + require actual active ptrace attachment. + + Defaults to the traditional behavior (for now) + +config PROC_MEM_ALWAYS_FORCE + bool "Traditional /proc/pid/mem behavior" + help + This allows /proc/pid/mem accesses to override memory mapping + permissions if you have ptrace access rights. + +config PROC_MEM_FORCE_PTRACE + bool "Require active ptrace() use for access override" + help + This allows /proc/pid/mem accesses to override memory mapping + permissions for active ptracers like gdb. + +config PROC_MEM_NO_FORCE + bool "Never" + help + Never override memory mapping permissions + +endchoice + config SECURITY bool "Enable different security models" depends on SYSFS -- cgit v1.2.3-58-ga151