Commit c6792d44 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'core_urgent_for_v5.11_rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull syscall entry fixes from Borislav Petkov:

 - For syscall user dispatch, separate prctl operation from syscall
   redirection range specification before the API has been made official
   in 5.11.

 - Ensure tasks using the generic syscall code do trap after returning
   from a syscall when single-stepping is requested.

* tag 'core_urgent_for_v5.11_rc7' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  entry: Use different define for selector variable in SUD
  entry: Ensure trap after single-step on system call return
parents 6fed85df 36a6c843

Documentation/admin-guide/syscall-user-dispatch.rst

+2 −2
Original line number Diff line number Diff line
@@ -70,8 +70,8 @@ trampoline code on the vDSO, that trampoline is never intercepted. 
[selector] is a pointer to a char-sized region in the process memory

region, that provides a quick way to enable disable syscall redirection

thread-wide, without the need to invoke the kernel directly.  selector

can be set to PR_SYS_DISPATCH_ON or PR_SYS_DISPATCH_OFF.  Any other

value should terminate the program with a SIGSYS.

can be set to SYSCALL_DISPATCH_FILTER_ALLOW or SYSCALL_DISPATCH_FILTER_BLOCK.

Any other value should terminate the program with a SIGSYS.



Security Notes

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

arch/x86/include/asm/entry-common.h

+0 −2
Original line number Diff line number Diff line
@@ -43,8 +43,6 @@ static __always_inline void arch_check_user_regs(struct pt_regs *regs) 
}

#define arch_check_user_regs arch_check_user_regs



#define ARCH_SYSCALL_EXIT_WORK		(_TIF_SINGLESTEP)



static inline void arch_exit_to_user_mode_prepare(struct pt_regs *regs,

						  unsigned long ti_work)

{

arch/x86/kernel/step.c

+8 −2
Original line number Diff line number Diff line
@@ -127,12 +127,17 @@ static int enable_single_step(struct task_struct *child) 
		regs->flags |= X86_EFLAGS_TF;



	/*

	 * Always set TIF_SINGLESTEP - this guarantees that

	 * we single-step system calls etc..  This will also

	 * Always set TIF_SINGLESTEP.  This will also

	 * cause us to set TF when returning to user mode.

	 */

	set_tsk_thread_flag(child, TIF_SINGLESTEP);



	/*

	 * Ensure that a trap is triggered once stepping out of a system

	 * call prior to executing any user instruction.

	 */

	set_task_syscall_work(child, SYSCALL_EXIT_TRAP);



	oflags = regs->flags;



	/* Set TF on the kernel stack.. */
@@ -230,6 +235,7 @@ void user_disable_single_step(struct task_struct *child) 


	/* Always clear TIF_SINGLESTEP... */

	clear_tsk_thread_flag(child, TIF_SINGLESTEP);

	clear_task_syscall_work(child, SYSCALL_EXIT_TRAP);



	/* But touch TF only if it was set by us.. */

	if (test_and_clear_tsk_thread_flag(child, TIF_FORCED_TF))

include/linux/entry-common.h

+1 −0
Original line number Diff line number Diff line
@@ -46,6 +46,7 @@ 
				 SYSCALL_WORK_SYSCALL_TRACE |		\

				 SYSCALL_WORK_SYSCALL_AUDIT |		\

				 SYSCALL_WORK_SYSCALL_USER_DISPATCH |	\

				 SYSCALL_WORK_SYSCALL_EXIT_TRAP	|	\

				 ARCH_SYSCALL_WORK_EXIT)



/*

include/linux/thread_info.h

+2 −0
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ enum syscall_work_bit { 
	SYSCALL_WORK_BIT_SYSCALL_EMU,

	SYSCALL_WORK_BIT_SYSCALL_AUDIT,

	SYSCALL_WORK_BIT_SYSCALL_USER_DISPATCH,

	SYSCALL_WORK_BIT_SYSCALL_EXIT_TRAP,

};



#define SYSCALL_WORK_SECCOMP		BIT(SYSCALL_WORK_BIT_SECCOMP)
@@ -51,6 +52,7 @@ enum syscall_work_bit { 
#define SYSCALL_WORK_SYSCALL_EMU	BIT(SYSCALL_WORK_BIT_SYSCALL_EMU)

#define SYSCALL_WORK_SYSCALL_AUDIT	BIT(SYSCALL_WORK_BIT_SYSCALL_AUDIT)

#define SYSCALL_WORK_SYSCALL_USER_DISPATCH BIT(SYSCALL_WORK_BIT_SYSCALL_USER_DISPATCH)

#define SYSCALL_WORK_SYSCALL_EXIT_TRAP	BIT(SYSCALL_WORK_BIT_SYSCALL_EXIT_TRAP)

#endif



#include <asm/thread_info.h>