[PATCH] exfat: preserve the 64-bit FITRIM minimum length

[PATCH] exfat: preserve the 64-bit FITRIM minimum length

[Hungyu Lin]

The FITRIM minimum length is a 64-bit value, but exfat_ioctl_fitrim()
uses max_t(unsigned int, ...) to compare it with the discard granularity.
This truncates the requested minimum on both 32-bit and 64-bit kernels.

For example, fstrim --minimum 4GiB can trim smaller free extents because
the minimum wraps to zero before being raised to the device granularity.

Use a u64 comparison to preserve the userspace value. exfat_trim_fs()
already stores the minimum cluster count in a u64.

Fixes: 654762df2ec7 ("exfat: add support ioctl and FITRIM function")
Cc: stable@vger.kernel.org
Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
---
 fs/exfat/file.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/exfat/file.c b/fs/exfat/file.c
index 1386149916bb..4e7a2fb30279 100644
--- a/fs/exfat/file.c
+++ b/fs/exfat/file.c
@@ -586,8 +586,8 @@ static int exfat_ioctl_fitrim(struct inode *inode, unsigned long arg)
 	if (copy_from_user(&range, (struct fstrim_range __user *)arg, sizeof(range)))
 		return -EFAULT;
 
-	range.minlen = max_t(unsigned int, range.minlen,
-				bdev_discard_granularity(inode->i_sb->s_bdev));
+	range.minlen = max_t(u64, range.minlen,
+			     bdev_discard_granularity(inode->i_sb->s_bdev));
 
 	ret = exfat_trim_fs(inode, &range);
 	if (ret < 0)
-- 
2.43.0

Re: [PATCH] exfat: preserve the 64-bit FITRIM minimum length

[Namjae Jeon]

On Sun, Nov 1, 2026 at 7:28 AM Hungyu Lin <dennylin0707@gmail.com> wrote:
>
> The FITRIM minimum length is a 64-bit value, but exfat_ioctl_fitrim()
> uses max_t(unsigned int, ...) to compare it with the discard granularity.
> This truncates the requested minimum on both 32-bit and 64-bit kernels.
>
> For example, fstrim --minimum 4GiB can trim smaller free extents because
> the minimum wraps to zero before being raised to the device granularity.
>
> Use a u64 comparison to preserve the userspace value. exfat_trim_fs()
> already stores the minimum cluster count in a u64.
>
> Fixes: 654762df2ec7 ("exfat: add support ioctl and FITRIM function")
> Cc: stable@vger.kernel.org
> Signed-off-by: Hungyu Lin <dennylin0707@gmail.com>
Applied it to #dev.
Thanks!