Commit 2404269b authored by Thomas Garnier's avatar Thomas Garnier Committed by Thomas Gleixner
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Revert "arm/syscalls: Check address limit on user-mode return" 



This reverts commit 73ac5d6a.

The work pending loop can call set_fs after addr_limit_user_check
removed the _TIF_FSCHECK flag. This may happen at anytime based on how
ARM handles alignment exceptions. It leads to an infinite loop condition.

After discussion, it has been agreed that the generic approach is not
tailored to the ARM architecture and any fix might not be complete. This
patch will be replaced by an architecture specific implementation. The
work flag approach will be kept for other architectures.

Reported-by: default avatarLeonard Crestez <leonard.crestez@nxp.com>
Signed-off-by: default avatarThomas Garnier <thgarnie@google.com>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Cc: Pratyush Anand <panand@redhat.com>
Cc: Dave Martin <Dave.Martin@arm.com>
Cc: Will Drewry <wad@chromium.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will.deacon@arm.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: David Howells <dhowells@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: linux-api@vger.kernel.org
Cc: Yonghong Song <yhs@fb.com>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1504798247-48833-3-git-send-email-keescook@chromium.org
parent bf29ed15

arch/arm/include/asm/thread_info.h

+6 −9
Original line number Diff line number Diff line
@@ -139,11 +139,10 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *, 
#define TIF_NEED_RESCHED	1	/* rescheduling necessary */

#define TIF_NOTIFY_RESUME	2	/* callback before returning to user */

#define TIF_UPROBE		3	/* breakpointed or singlestepping */

#define TIF_FSCHECK		4	/* Check FS is USER_DS on return */

#define TIF_SYSCALL_TRACE	5	/* syscall trace active */

#define TIF_SYSCALL_AUDIT	6	/* syscall auditing active */

#define TIF_SYSCALL_TRACEPOINT	7	/* syscall tracepoint instrumentation */

#define TIF_SECCOMP		8	/* seccomp syscall filtering active */

#define TIF_SYSCALL_TRACE	4	/* syscall trace active */

#define TIF_SYSCALL_AUDIT	5	/* syscall auditing active */

#define TIF_SYSCALL_TRACEPOINT	6	/* syscall tracepoint instrumentation */

#define TIF_SECCOMP		7	/* seccomp syscall filtering active */



#define TIF_NOHZ		12	/* in adaptive nohz mode */

#define TIF_USING_IWMMXT	17
@@ -154,7 +153,6 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *, 
#define _TIF_NEED_RESCHED	(1 << TIF_NEED_RESCHED)

#define _TIF_NOTIFY_RESUME	(1 << TIF_NOTIFY_RESUME)

#define _TIF_UPROBE		(1 << TIF_UPROBE)

#define _TIF_FSCHECK		(1 << TIF_FSCHECK)

#define _TIF_SYSCALL_TRACE	(1 << TIF_SYSCALL_TRACE)

#define _TIF_SYSCALL_AUDIT	(1 << TIF_SYSCALL_AUDIT)

#define _TIF_SYSCALL_TRACEPOINT	(1 << TIF_SYSCALL_TRACEPOINT)
@@ -169,8 +167,7 @@ extern int vfp_restore_user_hwstate(struct user_vfp __user *, 
 * Change these and you break ASM code in entry-common.S

 */

#define _TIF_WORK_MASK		(_TIF_NEED_RESCHED | _TIF_SIGPENDING | \

				 _TIF_NOTIFY_RESUME | _TIF_UPROBE |	\

				 _TIF_FSCHECK)

				 _TIF_NOTIFY_RESUME | _TIF_UPROBE)



#endif /* __KERNEL__ */

#endif /* __ASM_ARM_THREAD_INFO_H */

arch/arm/include/asm/uaccess.h

+0 −2
Original line number Diff line number Diff line
@@ -70,8 +70,6 @@ static inline void set_fs(mm_segment_t fs) 
{

	current_thread_info()->addr_limit = fs;

	modify_domain(DOMAIN_KERNEL, fs ? DOMAIN_CLIENT : DOMAIN_MANAGER);

	/* On user-mode return, check fs is correct */

	set_thread_flag(TIF_FSCHECK);

}



#define segment_eq(a, b)	((a) == (b))

arch/arm/kernel/entry-common.S

+2 −7
Original line number Diff line number Diff line
@@ -49,9 +49,7 @@ ret_fast_syscall: 
 UNWIND(.cantunwind	)

	disable_irq_notrace			@ disable interrupts

	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing

	tst	r1, #_TIF_SYSCALL_WORK

	bne	fast_work_pending

	tst	r1, #_TIF_WORK_MASK

	tst	r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK

	bne	fast_work_pending



	/* perform architecture specific actions before user return */
@@ -77,15 +75,12 @@ ret_fast_syscall: 
	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0

	disable_irq_notrace			@ disable interrupts

	ldr	r1, [tsk, #TI_FLAGS]		@ re-check for syscall tracing

	tst	r1, #_TIF_SYSCALL_WORK

	bne	fast_work_pending

	tst	r1, #_TIF_WORK_MASK

	tst	r1, #_TIF_SYSCALL_WORK | _TIF_WORK_MASK

	beq	no_work_pending

 UNWIND(.fnend		)

ENDPROC(ret_fast_syscall)



	/* Slower path - fall through to work_pending */

fast_work_pending:

#endif



	tst	r1, #_TIF_SYSCALL_WORK

arch/arm/kernel/signal.c

+0 −5
Original line number Diff line number Diff line
@@ -14,7 +14,6 @@ 
#include <linux/uaccess.h>

#include <linux/tracehook.h>

#include <linux/uprobes.h>

#include <linux/syscalls.h>



#include <asm/elf.h>

#include <asm/cacheflush.h>
@@ -614,10 +613,6 @@ do_work_pending(struct pt_regs *regs, unsigned int thread_flags, int syscall) 
	 * Update the trace code with the current status.

	 */

	trace_hardirqs_off();



	/* Check valid user FS if needed */

	addr_limit_user_check();



	do {

		if (likely(thread_flags & _TIF_NEED_RESCHED)) {

			schedule();

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