[GIT PULL] syscall-return address-limit checking fixes

From: Ingo Molnar
Date: Sun Sep 24 2017 - 07:17:59 EST

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Linus,

Please pull the latest core-urgent-for-linus git tree from:

git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git core-urgent-for-linus

# HEAD: a2048e34d4655c06d31400646ae495bbfeb16b27 arm64/syscalls: Move address limit check in loop

This fixes a number of bugs in the address-limit (USER_DS) checks that got
introduced in the merge window, (mostly) affecting the ARM and ARM64 platforms.

Thanks,

Ingo

------------------>
Thomas Garnier (4):
syscalls: Use CHECK_DATA_CORRUPTION for addr_limit_user_check
Revert "arm/syscalls: Check address limit on user-mode return"
arm/syscalls: Optimize address limit check
arm64/syscalls: Move address limit check in loop

arch/arm/include/asm/thread_info.h | 15 ++++++---------
arch/arm/include/asm/uaccess.h | 2 --
arch/arm/kernel/entry-common.S | 20 +++++++++++++-------
arch/arm/kernel/signal.c | 10 ++++++----
arch/arm64/kernel/signal.c | 6 +++---
include/linux/syscalls.h | 12 ++++++++----
6 files changed, 36 insertions(+), 29 deletions(-)

diff --git a/arch/arm/include/asm/thread_info.h b/arch/arm/include/asm/thread_info.h
index 1d468b527b7b..776757d1604a 100644
--- a/arch/arm/include/asm/thread_info.h
+++ b/arch/arm/include/asm/thread_info.h
@@ -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)
@@ -168,9 +166,8 @@ 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)
+#define _TIF_WORK_MASK (_TIF_NEED_RESCHED | _TIF_SIGPENDING | \
+ _TIF_NOTIFY_RESUME | _TIF_UPROBE)

#endif /* __KERNEL__ */
#endif /* __ASM_ARM_THREAD_INFO_H */
diff --git a/arch/arm/include/asm/uaccess.h b/arch/arm/include/asm/uaccess.h
index 87936dd5d151..0bf2347495f1 100644
--- a/arch/arm/include/asm/uaccess.h
+++ b/arch/arm/include/asm/uaccess.h
@@ -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))
diff --git a/arch/arm/kernel/entry-common.S b/arch/arm/kernel/entry-common.S
index ca3614dc6938..99c908226065 100644
--- a/arch/arm/kernel/entry-common.S
+++ b/arch/arm/kernel/entry-common.S
@@ -12,6 +12,7 @@
#include <asm/unistd.h>
#include <asm/ftrace.h>
#include <asm/unwind.h>
+#include <asm/memory.h>
#ifdef CONFIG_AEABI
#include <asm/unistd-oabi.h>
#endif
@@ -48,12 +49,14 @@ saved_pc .req lr
UNWIND(.fnstart )
UNWIND(.cantunwind )
disable_irq_notrace @ disable interrupts
+ ldr r2, [tsk, #TI_ADDR_LIMIT]
+ cmp r2, #TASK_SIZE
+ blne addr_limit_check_failed
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 */
arch_ret_to_user r1, lr

@@ -76,16 +79,16 @@ ENDPROC(ret_fast_syscall)
UNWIND(.cantunwind )
str r0, [sp, #S_R0 + S_OFF]! @ save returned r0
disable_irq_notrace @ disable interrupts
+ ldr r2, [tsk, #TI_ADDR_LIMIT]
+ cmp r2, #TASK_SIZE
+ blne addr_limit_check_failed
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
@@ -111,6 +114,9 @@ ENTRY(ret_to_user)
ret_slow_syscall:
disable_irq_notrace @ disable interrupts
ENTRY(ret_to_user_from_irq)
+ ldr r2, [tsk, #TI_ADDR_LIMIT]
+ cmp r2, #TASK_SIZE
+ blne addr_limit_check_failed
ldr r1, [tsk, #TI_FLAGS]
tst r1, #_TIF_WORK_MASK
bne slow_work_pending
diff --git a/arch/arm/kernel/signal.c b/arch/arm/kernel/signal.c
index e2de50bf8742..b67ae12503f3 100644
--- a/arch/arm/kernel/signal.c
+++ b/arch/arm/kernel/signal.c
@@ -614,10 +614,6 @@ 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();
@@ -678,3 +674,9 @@ struct page *get_signal_page(void)

return page;
}
+
+/* Defer to generic check */
+asmlinkage void addr_limit_check_failed(void)
+{
+ addr_limit_user_check();
+}
diff --git a/arch/arm64/kernel/signal.c b/arch/arm64/kernel/signal.c
index c45214f8fb54..0bdc96c61bc0 100644
--- a/arch/arm64/kernel/signal.c
+++ b/arch/arm64/kernel/signal.c
@@ -751,10 +751,10 @@ asmlinkage void do_notify_resume(struct pt_regs *regs,
*/
trace_hardirqs_off();

- /* Check valid user FS if needed */
- addr_limit_user_check();
-
do {
+ /* Check valid user FS if needed */
+ addr_limit_user_check();
+
if (thread_flags & _TIF_NEED_RESCHED) {
schedule();
} else {
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 95606a2d556f..a78186d826d7 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -221,21 +221,25 @@ static inline int is_syscall_trace_event(struct trace_event_call *tp_event)
} \
static inline long SYSC##name(__MAP(x,__SC_DECL,__VA_ARGS__))

-#ifdef TIF_FSCHECK
/*
* Called before coming back to user-mode. Returning to user-mode with an
* address limit different than USER_DS can allow to overwrite kernel memory.
*/
static inline void addr_limit_user_check(void)
{
-
+#ifdef TIF_FSCHECK
if (!test_thread_flag(TIF_FSCHECK))
return;
+#endif

- BUG_ON(!segment_eq(get_fs(), USER_DS));
+ if (CHECK_DATA_CORRUPTION(!segment_eq(get_fs(), USER_DS),
+ "Invalid address limit on user-mode return"))
+ force_sig(SIGKILL, current);
+
+#ifdef TIF_FSCHECK
clear_thread_flag(TIF_FSCHECK);
-}
#endif
+}

asmlinkage long sys32_quotactl(unsigned int cmd, const char __user *special,
qid_t id, void __user *addr);

Next message: Ingo Molnar: "[GIT PULL] IRQ fixes"
Previous message: yuzhoujian: "[PATCH v2 4/4] Make all print functions receive the fp argument, and opens a dump file in process_event."
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