| From: Arnd Bergmann <arnd@arndb.de> |
| Subject: mm/damon/dbgfs: fix bogus string length |
| Date: Fri, 2 Feb 2024 13:43:26 +0100 |
| |
| gcc correctly points out that using strnlen() on a fixed size array |
| is nonsense with an overlong limit: |
| |
| mm/damon/dbgfs.c: In function 'damon_dbgfs_deprecated_read': |
| mm/damon/dbgfs.c:814:19: error: 'strnlen' specified bound 1024 exceeds source size 512 [-Werror=stringop-overread] |
| 814 | int len = strnlen(kbuf, 1024); |
| | ^~~~~~~~~~~~~~~~~~~ |
| mm/damon/dbgfs.c:813:14: note: source object allocated here |
| 813 | char kbuf[512] = DAMON_DBGFS_DEPRECATION_NOTICE; |
| | ^~~~ |
| |
| In fact, neither of the arbitrary limits are needed here: The first |
| one can just be a static const string and avoid wasting any more |
| space then necessary, and the strnlen() can be either strlen() or |
| sizeof(kbuf)-1, both of which the compiler turns into the same |
| constant here. |
| |
| Link: https://lkml.kernel.org/r/20240202124339.892862-1-arnd@kernel.org |
| Fixes: adf9047adfff ("mm/damon/dbgfs: implement deprecation notice file") |
| Signed-off-by: Arnd Bergmann <arnd@arndb.de> |
| Reviewed-by: SeongJae Park <sj@kernel.org> |
| Cc: Alex Shi <alexs@kernel.org> |
| Cc: Hu Haowen <2023002089@link.tyut.edu.cn> |
| Cc: Jonathan Corbet <corbet@lwn.net> |
| Cc: Shuah Khan <shuah@kernel.org> |
| Cc: Yanteng Si <siyanteng@loongson.cn> |
| Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
| --- |
| |
| mm/damon/dbgfs.c | 5 ++--- |
| 1 file changed, 2 insertions(+), 3 deletions(-) |
| |
| --- a/mm/damon/dbgfs.c~mm-damon-dbgfs-implement-deprecation-notice-file-fix |
| +++ a/mm/damon/dbgfs.c |
| @@ -808,13 +808,12 @@ static void dbgfs_destroy_ctx(struct dam |
| static ssize_t damon_dbgfs_deprecated_read(struct file *file, |
| char __user *buf, size_t count, loff_t *ppos) |
| { |
| - char kbuf[512] = "DAMON debugfs interface is deprecated, " |
| + static const char kbuf[512] = "DAMON debugfs interface is deprecated, " |
| "so users should move to DAMON_SYSFS. If you cannot, " |
| "please report your usecase to damon@lists.linux.dev and " |
| "linux-mm@kvack.org.\n"; |
| - int len = strnlen(kbuf, 1024); |
| |
| - return simple_read_from_buffer(buf, count, ppos, kbuf, len); |
| + return simple_read_from_buffer(buf, count, ppos, kbuf, strlen(kbuf)); |
| } |
| |
| /* |
| _ |
