[axboe:rw_iter 496/525] drivers/acpi/proc.c:100 acpi_system_write_wakeup_device() warn: potential spectre issue 'strbuf' [w]

[axboe:rw_iter 496/525] drivers/acpi/proc.c:100 acpi_system_write_wakeup_device() warn: potential spectre issue 'strbuf' [w]

[kernel test robot]

BCC: lkp@intel.com
CC: oe-kbuild-all@lists.linux.dev
TO: Jens Axboe <axboe@kernel.dk>

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git rw_iter
head:   d5f290ca006c2bdabff8aa383fd3cf9cf9194259
commit: 231ea82faf415697c02c65ecb06a61d77a0953be [496/525] ACPI: convert proc_write to ->proc_write_iter()
:::::: branch date: 21 hours ago
:::::: commit date: 21 hours ago
config: x86_64-randconfig-161-20260326 (https://download.01.org/0day-ci/archive/20260326/202603261940.bDKprUrW-lkp@intel.com/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
smatch: v0.5.0-9004-gb810ac53

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202603261940.bDKprUrW-lkp@intel.com/

smatch warnings:
drivers/acpi/proc.c:100 acpi_system_write_wakeup_device() warn: potential spectre issue 'strbuf' [w]

vim +/strbuf +100 drivers/acpi/proc.c

76acae04c89228 drivers/acpi/sleep/proc.c Rafael J. Wysocki 2008-10-03   86  
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16   87  static ssize_t
231ea82faf4156 drivers/acpi/proc.c       Jens Axboe        2026-03-18   88  acpi_system_write_wakeup_device(struct kiocb *iocb, struct iov_iter *from)
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16   89  {
07761a4cd43c1d drivers/acpi/proc.c       chenqiwu          2020-02-23   90  	struct acpi_device *dev, *tmp;
231ea82faf4156 drivers/acpi/proc.c       Jens Axboe        2026-03-18   91  	size_t count = iov_iter_count(from);
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16   92  	char strbuf[5];
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16   93  	char str[5] = "";
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16   94  
05bce79e6d24ee drivers/acpi/proc.c       Cyril Roelandt    2012-11-22   95  	if (count > 4)
05bce79e6d24ee drivers/acpi/proc.c       Cyril Roelandt    2012-11-22   96  		count = 4;
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16   97  
231ea82faf4156 drivers/acpi/proc.c       Jens Axboe        2026-03-18   98  	if (!copy_from_iter_full(strbuf, count, from))
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16   99  		return -EFAULT;
05bce79e6d24ee drivers/acpi/proc.c       Cyril Roelandt    2012-11-22 @100  	strbuf[count] = '\0';
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16  101  	sscanf(strbuf, "%s", str);
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16  102  
9090589d87506c drivers/acpi/proc.c       Shaohua Li        2009-04-07  103  	mutex_lock(&acpi_device_lock);
07761a4cd43c1d drivers/acpi/proc.c       chenqiwu          2020-02-23  104  	list_for_each_entry_safe(dev, tmp, &acpi_wakeup_device_list,
07761a4cd43c1d drivers/acpi/proc.c       chenqiwu          2020-02-23  105  				 wakeup_list) {
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16  106  		if (!dev->wakeup.flags.valid)
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16  107  			continue;
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16  108  
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16  109  		if (!strncmp(dev->pnp.bus_id, str, 4)) {
f2b56bc808addb drivers/acpi/proc.c       Rafael J. Wysocki 2011-01-06  110  			if (device_can_wakeup(&dev->dev)) {
f2b56bc808addb drivers/acpi/proc.c       Rafael J. Wysocki 2011-01-06  111  				bool enable = !device_may_wakeup(&dev->dev);
f2b56bc808addb drivers/acpi/proc.c       Rafael J. Wysocki 2011-01-06  112  				device_set_wakeup_enable(&dev->dev, enable);
f2b56bc808addb drivers/acpi/proc.c       Rafael J. Wysocki 2011-01-06  113  			} else {
76acae04c89228 drivers/acpi/sleep/proc.c Rafael J. Wysocki 2008-10-03  114  				physical_device_enable_wakeup(dev);
f2b56bc808addb drivers/acpi/proc.c       Rafael J. Wysocki 2011-01-06  115  			}
b014f4f1aad3f2 drivers/acpi/proc.c       Rafael J. Wysocki 2011-01-06  116  			break;
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16  117  		}
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16  118  	}
9090589d87506c drivers/acpi/proc.c       Shaohua Li        2009-04-07  119  	mutex_unlock(&acpi_device_lock);
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16  120  	return count;
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16  121  }
^1da177e4c3f41 drivers/acpi/sleep/proc.c Linus Torvalds    2005-04-16  122  

:::::: The code at line 100 was first introduced by commit
:::::: 05bce79e6d24ee6eb2beddf0f6314358404d472f ACPI: drop unnecessary local variable from acpi_system_write_wakeup_device()

:::::: TO: Cyril Roelandt <tipecaml@gmail.com>
:::::: CC: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

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https://github.com/intel/lkp-tests/wiki