| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20251125-erlenholz-pausieren-0a4b80f2be6c@brauner>
Date: Tue, 25 Nov 2025 10:06:49 +0100
From: Christian Brauner <brauner@...nel.org>
To: david.laight.linux@...il.com
Cc: linux-kernel@...r.kernel.org, linux-ext4@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-mm@...ck.org, Alexander Viro <viro@...iv.linux.org.uk>,
Andreas Dilger <adilger.kernel@...ger.ca>, Kees Cook <kees@...nel.org>, Miklos Szeredi <miklos@...redi.hu>,
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>, Theodore Ts'o <tytso@....edu>
Subject: Re: [PATCH 30/44] fs: use min() or umin() instead of min_t()
On Wed, Nov 19, 2025 at 10:41:26PM +0000, david.laight.linux@...il.com wrote:
> From: David Laight <david.laight.linux@...il.com>
>
> min_t(unsigned int, a, b) casts an 'unsigned long' to 'unsigned int'.
> Use min(a, b) instead as it promotes any 'unsigned int' to 'unsigned long'
> and so cannot discard significant bits.
>
> A couple of places need umin() because of loops like:
> nfolios = DIV_ROUND_UP(ret + start, PAGE_SIZE);
>
> for (i = 0; i < nfolios; i++) {
> struct folio *folio = page_folio(pages[i]);
> ...
> unsigned int len = umin(ret, PAGE_SIZE - start);
> ...
> ret -= len;
> ...
> }
> where the compiler doesn't track things well enough to know that
> 'ret' is never negative.
>
> The alternate loop:
> for (i = 0; ret > 0; i++) {
> struct folio *folio = page_folio(pages[i]);
> ...
> unsigned int len = min(ret, PAGE_SIZE - start);
> ...
> ret -= len;
> ...
> }
> would be equivalent and doesn't need 'nfolios'.
>
> Most of the 'unsigned long' actually come from PAGE_SIZE.
>
> Detected by an extra check added to min_t().
>
> Signed-off-by: David Laight <david.laight.linux@...il.com>
> ---
Too late for this cycle but we will pick this up next cycle!
> fs/buffer.c | 2 +-
> fs/exec.c | 2 +-
> fs/ext4/mballoc.c | 3 +--
> fs/ext4/resize.c | 2 +-
> fs/ext4/super.c | 2 +-
> fs/fat/dir.c | 4 ++--
> fs/fat/file.c | 3 +--
> fs/fuse/dev.c | 2 +-
> fs/fuse/file.c | 8 +++-----
> fs/splice.c | 2 +-
> 10 files changed, 13 insertions(+), 17 deletions(-)
>
> diff --git a/fs/buffer.c b/fs/buffer.c
> index 6a8752f7bbed..26c4c760b6c6 100644
> --- a/fs/buffer.c
> +++ b/fs/buffer.c
> @@ -2354,7 +2354,7 @@ bool block_is_partially_uptodate(struct folio *folio, size_t from, size_t count)
> if (!head)
> return false;
> blocksize = head->b_size;
> - to = min_t(unsigned, folio_size(folio) - from, count);
> + to = min(folio_size(folio) - from, count);
> to = from + to;
> if (from < blocksize && to > folio_size(folio) - blocksize)
> return false;
> diff --git a/fs/exec.c b/fs/exec.c
> index 4298e7e08d5d..6d699e48df82 100644
> --- a/fs/exec.c
> +++ b/fs/exec.c
> @@ -555,7 +555,7 @@ int copy_string_kernel(const char *arg, struct linux_binprm *bprm)
> return -E2BIG;
>
> while (len > 0) {
> - unsigned int bytes_to_copy = min_t(unsigned int, len,
> + unsigned int bytes_to_copy = min(len,
> min_not_zero(offset_in_page(pos), PAGE_SIZE));
> struct page *page;
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index 9087183602e4..cb68ea974de6 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -4254,8 +4254,7 @@ void ext4_mb_mark_bb(struct super_block *sb, ext4_fsblk_t block,
> * get the corresponding group metadata to work with.
> * For this we have goto again loop.
> */
> - thisgrp_len = min_t(unsigned int, (unsigned int)len,
> - EXT4_BLOCKS_PER_GROUP(sb) - EXT4_C2B(sbi, blkoff));
> + thisgrp_len = min(len, EXT4_BLOCKS_PER_GROUP(sb) - EXT4_C2B(sbi, blkoff));
> clen = EXT4_NUM_B2C(sbi, thisgrp_len);
>
> if (!ext4_sb_block_valid(sb, NULL, block, thisgrp_len)) {
> diff --git a/fs/ext4/resize.c b/fs/ext4/resize.c
> index 050f26168d97..76842f0957b5 100644
> --- a/fs/ext4/resize.c
> +++ b/fs/ext4/resize.c
> @@ -1479,7 +1479,7 @@ static void ext4_update_super(struct super_block *sb,
>
> /* Update the global fs size fields */
> sbi->s_groups_count += flex_gd->count;
> - sbi->s_blockfile_groups = min_t(ext4_group_t, sbi->s_groups_count,
> + sbi->s_blockfile_groups = min(sbi->s_groups_count,
> (EXT4_MAX_BLOCK_FILE_PHYS / EXT4_BLOCKS_PER_GROUP(sb)));
>
> /* Update the reserved block counts only once the new group is
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 33e7c08c9529..e116fe48ff43 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -4830,7 +4830,7 @@ static int ext4_check_geometry(struct super_block *sb,
> return -EINVAL;
> }
> sbi->s_groups_count = blocks_count;
> - sbi->s_blockfile_groups = min_t(ext4_group_t, sbi->s_groups_count,
> + sbi->s_blockfile_groups = min(sbi->s_groups_count,
> (EXT4_MAX_BLOCK_FILE_PHYS / EXT4_BLOCKS_PER_GROUP(sb)));
> if (((u64)sbi->s_groups_count * sbi->s_inodes_per_group) !=
> le32_to_cpu(es->s_inodes_count)) {
> diff --git a/fs/fat/dir.c b/fs/fat/dir.c
> index 92b091783966..8375e7fbc1a5 100644
> --- a/fs/fat/dir.c
> +++ b/fs/fat/dir.c
> @@ -1353,7 +1353,7 @@ int fat_add_entries(struct inode *dir, void *slots, int nr_slots,
>
> /* Fill the long name slots. */
> for (i = 0; i < long_bhs; i++) {
> - int copy = min_t(int, sb->s_blocksize - offset, size);
> + int copy = umin(sb->s_blocksize - offset, size);
> memcpy(bhs[i]->b_data + offset, slots, copy);
> mark_buffer_dirty_inode(bhs[i], dir);
> offset = 0;
> @@ -1364,7 +1364,7 @@ int fat_add_entries(struct inode *dir, void *slots, int nr_slots,
> err = fat_sync_bhs(bhs, long_bhs);
> if (!err && i < nr_bhs) {
> /* Fill the short name slot. */
> - int copy = min_t(int, sb->s_blocksize - offset, size);
> + int copy = umin(sb->s_blocksize - offset, size);
> memcpy(bhs[i]->b_data + offset, slots, copy);
> mark_buffer_dirty_inode(bhs[i], dir);
> if (IS_DIRSYNC(dir))
> diff --git a/fs/fat/file.c b/fs/fat/file.c
> index 4fc49a614fb8..f48435e586c7 100644
> --- a/fs/fat/file.c
> +++ b/fs/fat/file.c
> @@ -140,8 +140,7 @@ static int fat_ioctl_fitrim(struct inode *inode, unsigned long arg)
> if (copy_from_user(&range, user_range, sizeof(range)))
> return -EFAULT;
>
> - range.minlen = max_t(unsigned int, range.minlen,
> - bdev_discard_granularity(sb->s_bdev));
> + range.minlen = max(range.minlen, bdev_discard_granularity(sb->s_bdev));
>
> err = fat_trim_fs(inode, &range);
> if (err < 0)
> diff --git a/fs/fuse/dev.c b/fs/fuse/dev.c
> index 132f38619d70..0c9fb0db1de1 100644
> --- a/fs/fuse/dev.c
> +++ b/fs/fuse/dev.c
> @@ -1813,7 +1813,7 @@ static int fuse_notify_store(struct fuse_conn *fc, unsigned int size,
> goto out_iput;
>
> folio_offset = ((index - folio->index) << PAGE_SHIFT) + offset;
> - nr_bytes = min_t(unsigned, num, folio_size(folio) - folio_offset);
> + nr_bytes = min(num, folio_size(folio) - folio_offset);
> nr_pages = (offset + nr_bytes + PAGE_SIZE - 1) >> PAGE_SHIFT;
>
> err = fuse_copy_folio(cs, &folio, folio_offset, nr_bytes, 0);
> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> index f1ef77a0be05..f4ffa559ad26 100644
> --- a/fs/fuse/file.c
> +++ b/fs/fuse/file.c
> @@ -1252,10 +1252,8 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
> static inline unsigned int fuse_wr_pages(loff_t pos, size_t len,
> unsigned int max_pages)
> {
> - return min_t(unsigned int,
> - ((pos + len - 1) >> PAGE_SHIFT) -
> - (pos >> PAGE_SHIFT) + 1,
> - max_pages);
> + return min(((pos + len - 1) >> PAGE_SHIFT) - (pos >> PAGE_SHIFT) + 1,
> + max_pages);
> }
>
> static ssize_t fuse_perform_write(struct kiocb *iocb, struct iov_iter *ii)
> @@ -1550,7 +1548,7 @@ static int fuse_get_user_pages(struct fuse_args_pages *ap, struct iov_iter *ii,
> struct folio *folio = page_folio(pages[i]);
> unsigned int offset = start +
> (folio_page_idx(folio, pages[i]) << PAGE_SHIFT);
> - unsigned int len = min_t(unsigned int, ret, PAGE_SIZE - start);
> + unsigned int len = umin(ret, PAGE_SIZE - start);
>
> ap->descs[ap->num_folios].offset = offset;
> ap->descs[ap->num_folios].length = len;
> diff --git a/fs/splice.c b/fs/splice.c
> index f5094b6d00a0..41ce3a4ef74f 100644
> --- a/fs/splice.c
> +++ b/fs/splice.c
> @@ -1467,7 +1467,7 @@ static ssize_t iter_to_pipe(struct iov_iter *from,
>
> n = DIV_ROUND_UP(left + start, PAGE_SIZE);
> for (i = 0; i < n; i++) {
> - int size = min_t(int, left, PAGE_SIZE - start);
> + int size = umin(left, PAGE_SIZE - start);
>
> buf.page = pages[i];
> buf.offset = start;
> --
> 2.39.5
>
Powered by blists - more mailing lists