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Subject[PATCH 1/9] pselect6() and friends: take handling the combined 6th/7th args into helper
Date
From: Al Viro <viro@zeniv.linux.org.uk>

... and use unsafe_get_user(), while we are at it.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
fs/select.c | 112 ++++++++++++++++++++++++++++++++++--------------------------
1 file changed, 64 insertions(+), 48 deletions(-)

diff --git a/fs/select.c b/fs/select.c
index 11d0285d46b7..7aef49552d4c 100644
--- a/fs/select.c
+++ b/fs/select.c
@@ -766,22 +766,38 @@ static long do_pselect(int n, fd_set __user *inp, fd_set __user *outp,
* which has a pointer to the sigset_t itself followed by a size_t containing
* the sigset size.
*/
+struct sigset_argpack {
+ sigset_t __user *p;
+ size_t size;
+};
+
+static inline int get_sigset_argpack(struct sigset_argpack *to,
+ struct sigset_argpack __user *from)
+{
+ // the path is hot enough for overhead of copy_from_user() to matter
+ if (from) {
+ if (!user_read_access_begin(from, sizeof(*from)))
+ return -EFAULT;
+ unsafe_get_user(to->p, &from->p, Efault);
+ unsafe_get_user(to->size, &from->size, Efault);
+ user_read_access_end();
+ }
+ return 0;
+Efault:
+ user_access_end();
+ return -EFAULT;
+}
+
SYSCALL_DEFINE6(pselect6, int, n, fd_set __user *, inp, fd_set __user *, outp,
fd_set __user *, exp, struct __kernel_timespec __user *, tsp,
void __user *, sig)
{
- size_t sigsetsize = 0;
- sigset_t __user *up = NULL;
-
- if (sig) {
- if (!access_ok(sig, sizeof(void *)+sizeof(size_t))
- || __get_user(up, (sigset_t __user * __user *)sig)
- || __get_user(sigsetsize,
- (size_t __user *)(sig+sizeof(void *))))
- return -EFAULT;
- }
+ struct sigset_argpack x = {NULL, 0};
+
+ if (get_sigset_argpack(&x, sig))
+ return -EFAULT;

- return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize, PT_TIMESPEC);
+ return do_pselect(n, inp, outp, exp, tsp, x.p, x.size, PT_TIMESPEC);
}

#if defined(CONFIG_COMPAT_32BIT_TIME) && !defined(CONFIG_64BIT)
@@ -790,18 +806,12 @@ SYSCALL_DEFINE6(pselect6_time32, int, n, fd_set __user *, inp, fd_set __user *,
fd_set __user *, exp, struct old_timespec32 __user *, tsp,
void __user *, sig)
{
- size_t sigsetsize = 0;
- sigset_t __user *up = NULL;
-
- if (sig) {
- if (!access_ok(sig, sizeof(void *)+sizeof(size_t))
- || __get_user(up, (sigset_t __user * __user *)sig)
- || __get_user(sigsetsize,
- (size_t __user *)(sig+sizeof(void *))))
- return -EFAULT;
- }
+ struct sigset_argpack x = {NULL, 0};
+
+ if (get_sigset_argpack(&x, sig))
+ return -EFAULT;

- return do_pselect(n, inp, outp, exp, tsp, up, sigsetsize, PT_OLD_TIMESPEC);
+ return do_pselect(n, inp, outp, exp, tsp, x.p, x.size, PT_OLD_TIMESPEC);
}

#endif
@@ -1325,24 +1335,37 @@ static long do_compat_pselect(int n, compat_ulong_t __user *inp,
return poll_select_finish(&end_time, tsp, type, ret);
}

+struct compat_sigset_argpack {
+ compat_uptr_t p;
+ compat_size_t size;
+};
+static inline int get_compat_sigset_argpack(struct compat_sigset_argpack *to,
+ struct compat_sigset_argpack __user *from)
+{
+ if (from) {
+ if (!user_read_access_begin(from, sizeof(*from)))
+ return -EFAULT;
+ unsafe_get_user(to->p, &from->p, Efault);
+ unsafe_get_user(to->size, &from->size, Efault);
+ user_read_access_end();
+ }
+ return 0;
+Efault:
+ user_access_end();
+ return -EFAULT;
+}
+
COMPAT_SYSCALL_DEFINE6(pselect6_time64, int, n, compat_ulong_t __user *, inp,
compat_ulong_t __user *, outp, compat_ulong_t __user *, exp,
struct __kernel_timespec __user *, tsp, void __user *, sig)
{
- compat_size_t sigsetsize = 0;
- compat_uptr_t up = 0;
-
- if (sig) {
- if (!access_ok(sig,
- sizeof(compat_uptr_t)+sizeof(compat_size_t)) ||
- __get_user(up, (compat_uptr_t __user *)sig) ||
- __get_user(sigsetsize,
- (compat_size_t __user *)(sig+sizeof(up))))
- return -EFAULT;
- }
+ struct compat_sigset_argpack x = {0, 0};
+
+ if (get_compat_sigset_argpack(&x, sig))
+ return -EFAULT;

- return do_compat_pselect(n, inp, outp, exp, tsp, compat_ptr(up),
- sigsetsize, PT_TIMESPEC);
+ return do_compat_pselect(n, inp, outp, exp, tsp, compat_ptr(x.p),
+ x.size, PT_TIMESPEC);
}

#if defined(CONFIG_COMPAT_32BIT_TIME)
@@ -1351,20 +1374,13 @@ COMPAT_SYSCALL_DEFINE6(pselect6_time32, int, n, compat_ulong_t __user *, inp,
compat_ulong_t __user *, outp, compat_ulong_t __user *, exp,
struct old_timespec32 __user *, tsp, void __user *, sig)
{
- compat_size_t sigsetsize = 0;
- compat_uptr_t up = 0;
-
- if (sig) {
- if (!access_ok(sig,
- sizeof(compat_uptr_t)+sizeof(compat_size_t)) ||
- __get_user(up, (compat_uptr_t __user *)sig) ||
- __get_user(sigsetsize,
- (compat_size_t __user *)(sig+sizeof(up))))
- return -EFAULT;
- }
+ struct compat_sigset_argpack x = {0, 0};
+
+ if (get_compat_sigset_argpack(&x, sig))
+ return -EFAULT;

- return do_compat_pselect(n, inp, outp, exp, tsp, compat_ptr(up),
- sigsetsize, PT_OLD_TIMESPEC);
+ return do_compat_pselect(n, inp, outp, exp, tsp, compat_ptr(x.p),
+ x.size, PT_OLD_TIMESPEC);
}

#endif
--
2.11.0
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