From e8dd273d199f5bbe295a8e3d8b777c5505b6b2e1 Mon Sep 17 00:00:00 2001 From: Salah Triki Date: Thu, 17 Sep 2026 14:00:52 +0100 Subject: iio: proximity: isl29501: Fix return type of isl29501_register_write isl29501_register_write() was returning a u32 instead of an int. Since the function returns negative error codes (such as -ERANGE or return values from i2c_smbus_write_byte_data()), returning an unsigned integer type prevents callers from correctly checking for negative error conditions. Fix this by changing the function return type from u32 to int. This was found through manual code review. Fixes: 1c28799257bc ("iio: light: isl29501: Add support for the ISL29501 ToF sensor.") Signed-off-by: Salah Triki Reviewed-by: Joshua Crofts Cc: stable@vger.kernel.org Signed-off-by: Jonathan Cameron --- lib/strnlen_user.c | 129 +++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 129 insertions(+) create mode 100644 lib/strnlen_user.c (limited to 'lib/strnlen_user.c') diff --git a/lib/strnlen_user.c b/lib/strnlen_user.c new file mode 100644 index 000000000..4a6574b67 --- /dev/null +++ b/lib/strnlen_user.c @@ -0,0 +1,129 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include + +#include + +/* + * Do a strnlen, return length of string *with* final '\0'. + * 'count' is the user-supplied count, while 'max' is the + * address space maximum. + * + * Return 0 for exceptions (which includes hitting the address + * space maximum), or 'count+1' if hitting the user-supplied + * maximum count. + * + * NOTE! We can sometimes overshoot the user-supplied maximum + * if it fits in a aligned 'long'. The caller needs to check + * the return value against "> max". + */ +static __always_inline long do_strnlen_user(const char __user *src, unsigned long count, unsigned long max) +{ + const struct word_at_a_time constants = WORD_AT_A_TIME_CONSTANTS; + unsigned long align, res = 0; + unsigned long c; + + /* + * Do everything aligned. But that means that we + * need to also expand the maximum.. + */ + align = (sizeof(unsigned long) - 1) & (unsigned long)src; + src -= align; + max += align; + + unsafe_get_user(c, (unsigned long __user *)src, efault); + c |= aligned_byte_mask(align); + + for (;;) { + unsigned long data; + if (has_zero(c, &data, &constants)) { + data = prep_zero_mask(c, data, &constants); + data = create_zero_mask(data); + return res + find_zero(data) + 1 - align; + } + res += sizeof(unsigned long); + /* We already handled 'unsigned long' bytes. Did we do it all ? */ + if (unlikely(max <= sizeof(unsigned long))) + break; + max -= sizeof(unsigned long); + unsafe_get_user(c, (unsigned long __user *)(src+res), efault); + } + res -= align; + + /* + * Uhhuh. We hit 'max'. But was that the user-specified maximum + * too? If so, return the marker for "too long". + */ + if (res >= count) + return count+1; + + /* + * Nope: we hit the address space limit, and we still had more + * characters the caller would have wanted. That's 0. + */ +efault: + return 0; +} + +/** + * strnlen_user: - Get the size of a user string INCLUDING final NUL. + * @str: The string to measure. + * @count: Maximum count (including NUL character) + * + * Context: User context only. This function may sleep if pagefaults are + * enabled. + * + * Get the size of a NUL-terminated string in user space. + * + * Returns the size of the string INCLUDING the terminating NUL. + * If the string is too long, returns a number larger than @count. User + * has to check the return value against "> count". + * On exception (or invalid count), returns 0. + * + * NOTE! You should basically never use this function. There is + * almost never any valid case for using the length of a user space + * string, since the string can be changed at any time by other + * threads. Use "strncpy_from_user()" instead to get a stable copy + * of the string. + */ +long strnlen_user(const char __user *str, long count) +{ + unsigned long max_addr, src_addr; + + if (unlikely(count <= 0)) + return 0; + + if (can_do_masked_user_access()) { + long retval; + + str = masked_user_read_access_begin(str); + retval = do_strnlen_user(str, count, count); + user_read_access_end(); + return retval; + } + + max_addr = TASK_SIZE_MAX; + src_addr = (unsigned long)untagged_addr(str); + if (likely(src_addr < max_addr)) { + unsigned long max = max_addr - src_addr; + long retval; + + /* + * Truncate 'max' to the user-specified limit, so that + * we only have one limit we need to check in the loop + */ + if (max > count) + max = count; + + if (user_read_access_begin(str, max)) { + retval = do_strnlen_user(str, count, max); + user_read_access_end(); + return retval; + } + } + return 0; +} +EXPORT_SYMBOL(strnlen_user); -- cgit v1.3.1