Commit 93a16312 authored Aug 02, 2024 by Adrian Ratiu Committed by Wentao Guan Feb 26, 2025

proc: add config & param to block forcing mem writes

stable inclusion
from stable-v6.6.55
commit 8552508033b26803c673598c925257a5ea6f4d98
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/IB0MX4

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=8552508033b26803c673598c925257a5ea6f4d98

--------------------------------

[ Upstream commit 41e8149c8892ed1962bd15350b3c3e6e90cba7f4 ]

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 <dianders@chromium.org>
Cc: Jeff Xu <jeffxu@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Kees Cook <kees@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Adrian Ratiu <adrian.ratiu@collabora.com>
Link: https://lore.kernel.org/r/20240802080225.89408-1-adrian.ratiu@collabora.com


Signed-off-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
[ add config to openeuler_defconfig ]
(cherry picked from commit 8552508033b26803c673598c925257a5ea6f4d98)
Signed-off-by: Wentao Guan <guanwentao@uniontech.com>

parent cd1d0dc2

Documentation/admin-guide/kernel-parameters.txt

+10 −0

Original line number	Diff line number	Diff line
		@@ -4743,6 +4743,16 @@
		printk.time= Show timing data prefixed to each printk message line
		Format: <bool> (1/Y/y=enable, 0/N/n=disable)

		proc_mem.force_override= [KNL]
		Format: {always \| ptrace \| never}
		Traditionally /proc/pid/mem allows memory permissions to be
		overridden without restrictions. This option may be set to
		restrict that. Can be one of:
		- 'always': traditional behavior always allows mem overrides.
		- 'ptrace': only allow mem overrides for active ptracers.
		- 'never': never allow mem overrides.
		If not specified, default is the CONFIG_PROC_MEM_* choice.

		processor.max_cstate= [HW,ACPI]
		Limit processor to maximum C-state
		max_cstate=9 overrides any DMI blacklist limit.

arch/arm64/configs/openeuler_defconfig

+3 −0

Original line number	Diff line number	Diff line
		@@ -7313,6 +7313,9 @@ CONFIG_ENCRYPTED_KEYS=y
		# CONFIG_USER_DECRYPTED_DATA is not set
		# CONFIG_KEY_DH_OPERATIONS is not set
		# CONFIG_SECURITY_DMESG_RESTRICT is not set
		CONFIG_PROC_MEM_ALWAYS_FORCE=y
		# CONFIG_PROC_MEM_FORCE_PTRACE is not set
		# CONFIG_PROC_MEM_NO_FORCE is not set
		CONFIG_SECURITY=y
		CONFIG_SECURITYFS=y
		CONFIG_SECURITY_NETWORK=y

arch/powerpc/configs/openeuler_defconfig

+3 −0

Original line number	Diff line number	Diff line
		@@ -6856,6 +6856,9 @@ CONFIG_ENCRYPTED_KEYS=y
		# CONFIG_USER_DECRYPTED_DATA is not set
		# CONFIG_KEY_DH_OPERATIONS is not set
		# CONFIG_SECURITY_DMESG_RESTRICT is not set
		CONFIG_PROC_MEM_ALWAYS_FORCE=y
		# CONFIG_PROC_MEM_FORCE_PTRACE is not set
		# CONFIG_PROC_MEM_NO_FORCE is not set
		CONFIG_SECURITY=y
		CONFIG_SECURITY_WRITABLE_HOOKS=y
		CONFIG_SECURITYFS=y

arch/riscv/configs/openeuler_defconfig

+3 −0

Original line number	Diff line number	Diff line
		@@ -6560,6 +6560,9 @@ CONFIG_ENCRYPTED_KEYS=y
		# CONFIG_USER_DECRYPTED_DATA is not set
		# CONFIG_KEY_DH_OPERATIONS is not set
		# CONFIG_SECURITY_DMESG_RESTRICT is not set
		CONFIG_PROC_MEM_ALWAYS_FORCE=y
		# CONFIG_PROC_MEM_FORCE_PTRACE is not set
		# CONFIG_PROC_MEM_NO_FORCE is not set
		CONFIG_SECURITY=y
		CONFIG_SECURITYFS=y
		CONFIG_SECURITY_NETWORK=y

arch/x86/configs/openeuler_defconfig

+3 −0

Original line number	Diff line number	Diff line
		@@ -8488,6 +8488,9 @@ CONFIG_ENCRYPTED_KEYS=y
		# CONFIG_USER_DECRYPTED_DATA is not set
		# CONFIG_KEY_DH_OPERATIONS is not set
		# CONFIG_SECURITY_DMESG_RESTRICT is not set
		CONFIG_PROC_MEM_ALWAYS_FORCE=y
		# CONFIG_PROC_MEM_FORCE_PTRACE is not set
		# CONFIG_PROC_MEM_NO_FORCE is not set
		CONFIG_SECURITY=y
		CONFIG_SECURITYFS=y
		CONFIG_SECURITY_NETWORK=y