b24413180f560 (Greg Kroah-Hartman 2017-11-01 15:07:57 +0100 1) // SPDX-License-Identifier: GPL-2.0
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 2) #include <linux/kernel.h>
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 3) #include <linux/export.h>
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 4) #include <linux/uaccess.h>
903f433f8f7a3 (Andrey Konovalov 2019-09-25 16:48:27 -0700 5) #include <linux/mm.h>
f5a1a536fa148 (Aleksa Sarai 2019-10-01 11:10:52 +1000 6) #include <linux/bitops.h>
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 7)
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 8) #include <asm/word-at-a-time.h>
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 9)
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 10) /*
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 11) * Do a strnlen, return length of string *with* final '\0'.
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 12) * 'count' is the user-supplied count, while 'max' is the
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 13) * address space maximum.
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 14) *
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 15) * Return 0 for exceptions (which includes hitting the address
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 16) * space maximum), or 'count+1' if hitting the user-supplied
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 17) * maximum count.
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 18) *
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 19) * NOTE! We can sometimes overshoot the user-supplied maximum
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 20) * if it fits in a aligned 'long'. The caller needs to check
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 21) * the return value against "> max".
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 22) */
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 23) static inline long do_strnlen_user(const char __user *src, unsigned long count, unsigned long max)
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 24) {
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 25) const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS;
29da93fea3ea3 (Peter Zijlstra 2019-04-24 09:19:25 +0200 26) unsigned long align, res = 0;
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 27) unsigned long c;
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 28)
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 29) /*
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 30) * Do everything aligned. But that means that we
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 31) * need to also expand the maximum..
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 32) */
29da93fea3ea3 (Peter Zijlstra 2019-04-24 09:19:25 +0200 33) align = (sizeof(unsigned long) - 1) & (unsigned long)src;
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 34) src -= align;
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 35) max += align;
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 36)
1bd4403d86a1c (Linus Torvalds 2016-08-08 13:02:01 -0700 37) unsafe_get_user(c, (unsigned long __user *)src, efault);
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 38) c |= aligned_byte_mask(align);
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 39)
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 40) for (;;) {
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 41) unsigned long data;
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 42) if (has_zero(c, &data, &constants)) {
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 43) data = prep_zero_mask(c, data, &constants);
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 44) data = create_zero_mask(data);
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 45) return res + find_zero(data) + 1 - align;
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 46) }
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 47) res += sizeof(unsigned long);
f18c34e483ff6 (Jan Kara 2015-06-02 17:10:28 +0200 48) /* We already handled 'unsigned long' bytes. Did we do it all ? */
f18c34e483ff6 (Jan Kara 2015-06-02 17:10:28 +0200 49) if (unlikely(max <= sizeof(unsigned long)))
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 50) break;
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 51) max -= sizeof(unsigned long);
1bd4403d86a1c (Linus Torvalds 2016-08-08 13:02:01 -0700 52) unsafe_get_user(c, (unsigned long __user *)(src+res), efault);
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 53) }
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 54) res -= align;
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 55)
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 56) /*
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 57) * Uhhuh. We hit 'max'. But was that the user-specified maximum
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 58) * too? If so, return the marker for "too long".
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 59) */
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 60) if (res >= count)
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 61) return count+1;
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 62)
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 63) /*
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 64) * Nope: we hit the address space limit, and we still had more
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 65) * characters the caller would have wanted. That's 0.
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 66) */
1bd4403d86a1c (Linus Torvalds 2016-08-08 13:02:01 -0700 67) efault:
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 68) return 0;
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 69) }
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 70)
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 71) /**
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 72) * strnlen_user: - Get the size of a user string INCLUDING final NUL.
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 73) * @str: The string to measure.
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 74) * @count: Maximum count (including NUL character)
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 75) *
b3c395ef5556a (David Hildenbrand 2015-05-11 17:52:08 +0200 76) * Context: User context only. This function may sleep if pagefaults are
b3c395ef5556a (David Hildenbrand 2015-05-11 17:52:08 +0200 77) * enabled.
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 78) *
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 79) * Get the size of a NUL-terminated string in user space.
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 80) *
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 81) * Returns the size of the string INCLUDING the terminating NUL.
226a07ef0a5a2 (Jan Kara 2015-06-03 15:50:35 +0200 82) * If the string is too long, returns a number larger than @count. User
226a07ef0a5a2 (Jan Kara 2015-06-03 15:50:35 +0200 83) * has to check the return value against "> count".
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 84) * On exception (or invalid count), returns 0.
226a07ef0a5a2 (Jan Kara 2015-06-03 15:50:35 +0200 85) *
226a07ef0a5a2 (Jan Kara 2015-06-03 15:50:35 +0200 86) * NOTE! You should basically never use this function. There is
226a07ef0a5a2 (Jan Kara 2015-06-03 15:50:35 +0200 87) * almost never any valid case for using the length of a user space
226a07ef0a5a2 (Jan Kara 2015-06-03 15:50:35 +0200 88) * string, since the string can be changed at any time by other
226a07ef0a5a2 (Jan Kara 2015-06-03 15:50:35 +0200 89) * threads. Use "strncpy_from_user()" instead to get a stable copy
226a07ef0a5a2 (Jan Kara 2015-06-03 15:50:35 +0200 90) * of the string.
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 91) */
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 92) long strnlen_user(const char __user *str, long count)
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 93) {
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 94) unsigned long max_addr, src_addr;
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 95)
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 96) if (unlikely(count <= 0))
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 97) return 0;
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 98)
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 99) max_addr = user_addr_max();
903f433f8f7a3 (Andrey Konovalov 2019-09-25 16:48:27 -0700 100) src_addr = (unsigned long)untagged_addr(str);
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 101) if (likely(src_addr < max_addr)) {
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 102) unsigned long max = max_addr - src_addr;
9fd4470ff4974 (Linus Torvalds 2015-12-17 10:05:19 -0800 103) long retval;
9fd4470ff4974 (Linus Torvalds 2015-12-17 10:05:19 -0800 104)
ab10ae1c3bef5 (Christophe Leroy 2020-01-23 08:34:18 +0000 105) /*
ab10ae1c3bef5 (Christophe Leroy 2020-01-23 08:34:18 +0000 106) * Truncate 'max' to the user-specified limit, so that
ab10ae1c3bef5 (Christophe Leroy 2020-01-23 08:34:18 +0000 107) * we only have one limit we need to check in the loop
ab10ae1c3bef5 (Christophe Leroy 2020-01-23 08:34:18 +0000 108) */
ab10ae1c3bef5 (Christophe Leroy 2020-01-23 08:34:18 +0000 109) if (max > count)
ab10ae1c3bef5 (Christophe Leroy 2020-01-23 08:34:18 +0000 110) max = count;
ab10ae1c3bef5 (Christophe Leroy 2020-01-23 08:34:18 +0000 111)
41cd780524674 (Christophe Leroy 2020-04-03 07:20:51 +0000 112) if (user_read_access_begin(str, max)) {
594cc251fdd0d (Linus Torvalds 2019-01-04 12:56:09 -0800 113) retval = do_strnlen_user(str, count, max);
41cd780524674 (Christophe Leroy 2020-04-03 07:20:51 +0000 114) user_read_access_end();
594cc251fdd0d (Linus Torvalds 2019-01-04 12:56:09 -0800 115) return retval;
594cc251fdd0d (Linus Torvalds 2019-01-04 12:56:09 -0800 116) }
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 117) }
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 118) return 0;
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 119) }
a08c5356a3aaf (Linus Torvalds 2012-05-26 11:06:38 -0700 120) EXPORT_SYMBOL(strnlen_user);
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