[PATCH 14/14] uaccess: drop set_fs leftovers

Arnd Bergmann
2022-02-14T16:34:52Z

From: Arnd Bergmann <arnd@arndb.de>

There are no more users of CONFIG_SET_FS left, so drop all
remaining references to set_fs()/get_fs(), mm_segment_t
and uaccess_kernel().

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
arch/Kconfig | 3 ---
arch/arm/lib/uaccess_with_memcpy.c | 10 ---------
arch/nds32/kernel/process.c | 5 ++---
arch/parisc/include/asm/futex.h | 2 +-
arch/parisc/lib/memcpy.c | 2 +-
drivers/hid/uhid.c | 2 +-
drivers/scsi/sg.c | 5 -----
fs/exec.c | 6 ------
include/asm-generic/access_ok.h | 10 +--------
include/linux/syscalls.h | 4 ----
include/linux/uaccess.h | 33 ------------------------------
include/rdma/ib.h | 2 +-
kernel/events/callchain.c | 4 ----
kernel/events/core.c | 3 ---
kernel/exit.c | 14 -------------
kernel/kthread.c | 5 -----
kernel/stacktrace.c | 3 ---
kernel/trace/bpf_trace.c | 4 ----
mm/maccess.c | 11 ----------
mm/memory.c | 8 --------
net/bpfilter/bpfilter_kern.c | 2 +-
21 files changed, 8 insertions(+), 130 deletions(-)

diff --git a/arch/Kconfig b/arch/Kconfig
index 678a80713b21..96075a12c720 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -24,9 +24,6 @@ config KEXEC_ELF
config HAVE_IMA_KEXEC
bool

-config SET_FS
- bool
-
config HOTPLUG_SMT
bool

diff --git a/arch/arm/lib/uaccess_with_memcpy.c b/arch/arm/lib/uaccess_with_memcpy.c
index 106f83a5ea6d..c30b689bec2e 100644
--- a/arch/arm/lib/uaccess_with_memcpy.c
+++ b/arch/arm/lib/uaccess_with_memcpy.c
@@ -92,11 +92,6 @@ __copy_to_user_memcpy(void __user *to, const void *from, unsigned long n)
unsigned long ua_flags;
int atomic;

- if (uaccess_kernel()) {
- memcpy((void *)to, from, n);
- return 0;
- }
-
/* the mmap semaphore is taken only if not in an atomic context */
atomic = faulthandler_disabled();

@@ -165,11 +160,6 @@ __clear_user_memset(void __user *addr, unsigned long n)
{
unsigned long ua_flags;

- if (uaccess_kernel()) {
- memset((void *)addr, 0, n);
- return 0;
- }
-
mmap_read_lock(current->mm);
while (n) {
pte_t *pte;
diff --git a/arch/nds32/kernel/process.c b/arch/nds32/kernel/process.c
index 49fab9e39cbf..d35c1f63fa11 100644
--- a/arch/nds32/kernel/process.c
+++ b/arch/nds32/kernel/process.c
@@ -119,9 +119,8 @@ void show_regs(struct pt_regs *regs)
regs->uregs[7], regs->uregs[6], regs->uregs[5], regs->uregs[4]);
pr_info("r3 : %08lx r2 : %08lx r1 : %08lx r0 : %08lx\n",
regs->uregs[3], regs->uregs[2], regs->uregs[1], regs->uregs[0]);
- pr_info(" IRQs o%s Segment %s\n",
- interrupts_enabled(regs) ? "n" : "ff",
- uaccess_kernel() ? "kernel" : "user");
+ pr_info(" IRQs o%s Segment user\n",
+ interrupts_enabled(regs) ? "n" : "ff");
}

EXPORT_SYMBOL(show_regs);
diff --git a/arch/parisc/include/asm/futex.h b/arch/parisc/include/asm/futex.h
index b5835325d44b..2f4a1b1ef387 100644
--- a/arch/parisc/include/asm/futex.h
+++ b/arch/parisc/include/asm/futex.h
@@ -99,7 +99,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
/* futex.c wants to do a cmpxchg_inatomic on kernel NULL, which is
* our gateway page, and causes no end of trouble...
*/
- if (uaccess_kernel() && !uaddr)
+ if (!uaddr)
return -EFAULT;

if (!access_ok(uaddr, sizeof(u32)))
diff --git a/arch/parisc/lib/memcpy.c b/arch/parisc/lib/memcpy.c
index ea70a0e08321..468704ce8a1c 100644
--- a/arch/parisc/lib/memcpy.c
+++ b/arch/parisc/lib/memcpy.c
@@ -13,7 +13,7 @@
#include <linux/compiler.h>
#include <linux/uaccess.h>

-#define get_user_space() (uaccess_kernel() ? 0 : mfsp(3))
+#define get_user_space() (mfsp(3))
#define get_kernel_space() (0)

/* Returns 0 for success, otherwise, returns number of bytes not transferred. */
diff --git a/drivers/hid/uhid.c b/drivers/hid/uhid.c
index 614adb510dbd..2a918aeb0af1 100644
--- a/drivers/hid/uhid.c
+++ b/drivers/hid/uhid.c
@@ -747,7 +747,7 @@ static ssize_t uhid_char_write(struct file *file, const char __user *buffer,
* copied from, so it's unsafe to allow this with elevated
* privileges (e.g. from a setuid binary) or via kernel_write().
*/
- if (file->f_cred != current_cred() || uaccess_kernel()) {
+ if (file->f_cred != current_cred()) {
pr_err_once("UHID_CREATE from different security context by process %d (%s), this is not allowed.\n",
task_tgid_vnr(current), current->comm);
ret = -EACCES;
diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
index 6b43e97bd417..aaa2376b9d34 100644
--- a/drivers/scsi/sg.c
+++ b/drivers/scsi/sg.c
@@ -224,11 +224,6 @@ static int sg_check_file_access(struct file *filp, const char *caller)
caller, task_tgid_vnr(current), current->comm);
return -EPERM;
}
- if (uaccess_kernel()) {
- pr_err_once("%s: process %d (%s) called from kernel context, this is not allowed.\n",
- caller, task_tgid_vnr(current), current->comm);
- return -EACCES;
- }
return 0;
}

diff --git a/fs/exec.c b/fs/exec.c
index 79f2c9483302..bc68a0c089ac 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1303,12 +1303,6 @@ int begin_new_exec(struct linux_binprm * bprm)
if (retval)
goto out_unlock;

- /*
- * Ensure that the uaccess routines can actually operate on userspace
- * pointers:
- */
- force_uaccess_begin();
-
if (me->flags & PF_KTHREAD)
free_kthread_struct(me);
me->flags &= ~(PF_RANDOMIZE | PF_FORKNOEXEC | PF_KTHREAD |
diff --git a/include/asm-generic/access_ok.h b/include/asm-generic/access_ok.h
index 883b573af5fe..725647ba8ea9 100644
--- a/include/asm-generic/access_ok.h
+++ b/include/asm-generic/access_ok.h
@@ -16,16 +16,8 @@
#define TASK_SIZE_MAX TASK_SIZE
#endif

-#ifndef uaccess_kernel
-#ifdef CONFIG_SET_FS
-#define uaccess_kernel() (get_fs().seg == KERNEL_DS.seg)
-#else
-#define uaccess_kernel() (0)
-#endif
-#endif
-
#ifndef user_addr_max
-#define user_addr_max() (uaccess_kernel() ? ~0UL : TASK_SIZE_MAX)
+#define user_addr_max() TASK_SIZE_MAX
#endif

#ifndef __access_ok
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 819c0cb00b6d..a34b0f9a9972 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -290,10 +290,6 @@ static inline void addr_limit_user_check(void)
return;
#endif

- if (CHECK_DATA_CORRUPTION(uaccess_kernel(),
- "Invalid address limit on user-mode return"))
- force_sig(SIGKILL);
-
#ifdef TIF_FSCHECK
clear_thread_flag(TIF_FSCHECK);
#endif
diff --git a/include/linux/uaccess.h b/include/linux/uaccess.h
index 2c31667e62e0..2421a41f3a8e 100644
--- a/include/linux/uaccess.h
+++ b/include/linux/uaccess.h
@@ -10,39 +10,6 @@

#include <asm/uaccess.h>

-#ifdef CONFIG_SET_FS
-/*
- * Force the uaccess routines to be wired up for actual userspace access,
- * overriding any possible set_fs(KERNEL_DS) still lingering around. Undone
- * using force_uaccess_end below.
- */
-static inline mm_segment_t force_uaccess_begin(void)
-{
- mm_segment_t fs = get_fs();
-
- set_fs(USER_DS);
- return fs;
-}
-
-static inline void force_uaccess_end(mm_segment_t oldfs)
-{
- set_fs(oldfs);
-}
-#else /* CONFIG_SET_FS */
-typedef struct {
- /* empty dummy */
-} mm_segment_t;
-
-static inline mm_segment_t force_uaccess_begin(void)
-{
- return (mm_segment_t) { };
-}
-
-static inline void force_uaccess_end(mm_segment_t oldfs)
-{
-}
-#endif /* CONFIG_SET_FS */
-
/*
* Architectures should provide two primitives (raw_copy_{to,from}_user())
* and get rid of their private instances of copy_{to,from}_user() and
diff --git a/include/rdma/ib.h b/include/rdma/ib.h
index 83139b9ce409..f7c185ff7a11 100644
--- a/include/rdma/ib.h
+++ b/include/rdma/ib.h
@@ -75,7 +75,7 @@ struct sockaddr_ib {
*/
static inline bool ib_safe_file_access(struct file *filp)
{
- return filp->f_cred == current_cred() && !uaccess_kernel();
+ return filp->f_cred == current_cred();
}

#endif /* _RDMA_IB_H */
diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index 58cbe357fb2b..1273be84392c 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -209,17 +209,13 @@ get_perf_callchain(struct pt_regs *regs, u32 init_nr, bool kernel, bool user,
}

if (regs) {
- mm_segment_t fs;
-
if (crosstask)
goto exit_put;

if (add_mark)
perf_callchain_store_context(&ctx, PERF_CONTEXT_USER);

- fs = force_uaccess_begin();
perf_callchain_user(&ctx, regs);
- force_uaccess_end(fs);
}
}

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 57c7197838db..11ca7303d6df 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -6746,7 +6746,6 @@ perf_output_sample_ustack(struct perf_output_handle *handle, u64 dump_size,
unsigned long sp;
unsigned int rem;
u64 dyn_size;
- mm_segment_t fs;

/*
* We dump:
@@ -6764,9 +6763,7 @@ perf_output_sample_ustack(struct perf_output_handle *handle, u64 dump_size,

/* Data. */
sp = perf_user_stack_pointer(regs);
- fs = force_uaccess_begin();
rem = __output_copy_user(handle, (void *) sp, dump_size);
- force_uaccess_end(fs);
dyn_size = dump_size - rem;

perf_output_skip(handle, rem);
diff --git a/kernel/exit.c b/kernel/exit.c
index b00a25bb4ab9..0884a75bc2f8 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -737,20 +737,6 @@ void __noreturn do_exit(long code)

WARN_ON(blk_needs_flush_plug(tsk));

- /*
- * If do_dead is called because this processes oopsed, it's possible
- * that get_fs() was left as KERNEL_DS, so reset it to USER_DS before
- * continuing. Amongst other possible reasons, this is to prevent
- * mm_release()->clear_child_tid() from writing to a user-controlled
- * kernel address.
- *
- * On uptodate architectures force_uaccess_begin is a noop. On
- * architectures that still have set_fs/get_fs in addition to handling
- * oopses handles kernel threads that run as set_fs(KERNEL_DS) by
- * default.
- */
- force_uaccess_begin();
-
kcov_task_exit(tsk);

coredump_task_exit(tsk);
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 38c6dd822da8..16c2275d4b50 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -55,7 +55,6 @@ struct kthread {
int result;
int (*threadfn)(void *);
void *data;
- mm_segment_t oldfs;
struct completion parked;
struct completion exited;
#ifdef CONFIG_BLK_CGROUP
@@ -1441,8 +1440,6 @@ void kthread_use_mm(struct mm_struct *mm)
mmdrop(active_mm);
else
smp_mb();
-
- to_kthread(tsk)->oldfs = force_uaccess_begin();
}
EXPORT_SYMBOL_GPL(kthread_use_mm);

@@ -1457,8 +1454,6 @@ void kthread_unuse_mm(struct mm_struct *mm)
WARN_ON_ONCE(!(tsk->flags & PF_KTHREAD));
WARN_ON_ONCE(!tsk->mm);

- force_uaccess_end(to_kthread(tsk)->oldfs);
-
task_lock(tsk);
/*
* When a kthread stops operating on an address space, the loop
diff --git a/kernel/stacktrace.c b/kernel/stacktrace.c
index 9c625257023d..9ed5ce989415 100644
--- a/kernel/stacktrace.c
+++ b/kernel/stacktrace.c
@@ -226,15 +226,12 @@ unsigned int stack_trace_save_user(unsigned long *store, unsigned int size)
.store = store,
.size = size,
};
- mm_segment_t fs;

/* Trace user stack if not a kernel thread */
if (current->flags & PF_KTHREAD)
return 0;

- fs = force_uaccess_begin();
arch_stack_walk_user(consume_entry, &c, task_pt_regs(current));
- force_uaccess_end(fs);

return c.len;
}
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
index 21aa30644219..8115fff17018 100644
--- a/kernel/trace/bpf_trace.c
+++ b/kernel/trace/bpf_trace.c
@@ -332,8 +332,6 @@ BPF_CALL_3(bpf_probe_write_user, void __user *, unsafe_ptr, const void *, src,
if (unlikely(in_interrupt() ||
current->flags & (PF_KTHREAD | PF_EXITING)))
return -EPERM;
- if (unlikely(uaccess_kernel()))
- return -EPERM;
if (unlikely(!nmi_uaccess_okay()))
return -EPERM;

@@ -835,8 +833,6 @@ static int bpf_send_signal_common(u32 sig, enum pid_type type)
*/
if (unlikely(current->flags & (PF_KTHREAD | PF_EXITING)))
return -EPERM;
- if (unlikely(uaccess_kernel()))
- return -EPERM;
if (unlikely(!nmi_uaccess_okay()))
return -EPERM;

diff --git a/mm/maccess.c b/mm/maccess.c
index cbd1b3959af2..106820b33a2b 100644
--- a/mm/maccess.c
+++ b/mm/maccess.c
@@ -113,14 +113,11 @@ long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr, long count)
long copy_from_user_nofault(void *dst, const void __user *src, size_t size)
{
long ret = -EFAULT;
- mm_segment_t old_fs = force_uaccess_begin();
-
if (access_ok(src, size)) {
pagefault_disable();
ret = __copy_from_user_inatomic(dst, src, size);
pagefault_enable();
}
- force_uaccess_end(old_fs);

if (ret)
return -EFAULT;
@@ -140,14 +137,12 @@ EXPORT_SYMBOL_GPL(copy_from_user_nofault);
long copy_to_user_nofault(void __user *dst, const void *src, size_t size)
{
long ret = -EFAULT;
- mm_segment_t old_fs = force_uaccess_begin();

if (access_ok(dst, size)) {
pagefault_disable();
ret = __copy_to_user_inatomic(dst, src, size);
pagefault_enable();
}
- force_uaccess_end(old_fs);

if (ret)
return -EFAULT;
@@ -176,17 +171,14 @@ EXPORT_SYMBOL_GPL(copy_to_user_nofault);
long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
long count)
{
- mm_segment_t old_fs;
long ret;

if (unlikely(count <= 0))
return 0;

- old_fs = force_uaccess_begin();
pagefault_disable();
ret = strncpy_from_user(dst, unsafe_addr, count);
pagefault_enable();
- force_uaccess_end(old_fs);

if (ret >= count) {
ret = count;
@@ -216,14 +208,11 @@ long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
*/
long strnlen_user_nofault(const void __user *unsafe_addr, long count)
{
- mm_segment_t old_fs;
int ret;

- old_fs = force_uaccess_begin();
pagefault_disable();
ret = strnlen_user(unsafe_addr, count);
pagefault_enable();
- force_uaccess_end(old_fs);

return ret;
}
diff --git a/mm/memory.c b/mm/memory.c
index c125c4969913..9a6ebf68a846 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -5256,14 +5256,6 @@ void print_vma_addr(char *prefix, unsigned long ip)
#if defined(CONFIG_PROVE_LOCKING) || defined(CONFIG_DEBUG_ATOMIC_SLEEP)
void __might_fault(const char *file, int line)
{
- /*
- * Some code (nfs/sunrpc) uses socket ops on kernel memory while
- * holding the mmap_lock, this is safe because kernel memory doesn't
- * get paged out, therefore we'll never actually fault, and the
- * below annotations will generate false positives.
- */
- if (uaccess_kernel())
- return;
if (pagefault_disabled())
return;
__might_sleep(file, line);
diff --git a/net/bpfilter/bpfilter_kern.c b/net/bpfilter/bpfilter_kern.c
index 51a941b56ec3..422ec6e7ccff 100644
--- a/net/bpfilter/bpfilter_kern.c
+++ b/net/bpfilter/bpfilter_kern.c
@@ -70,7 +70,7 @@ static int bpfilter_process_sockopt(struct sock *sk, int optname,
.addr = (uintptr_t)optval.user,
.len = optlen,
};
- if (uaccess_kernel() || sockptr_is_kernel(optval)) {
+ if (sockptr_is_kernel(optval)) {
pr_err("kernel access not supported\n");
return -EFAULT;
}
--
2.29.2