+ iov_iter-use-iov_offset-for-length-calculation-in-iov_iter_aligned_bvec.patch added to mm-hotfixes-unstable branch

+ iov_iter-use-iov_offset-for-length-calculation-in-iov_iter_aligned_bvec.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: iov_iter: use iov_offset for length calculation in iov_iter_aligned_bvec
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     iov_iter-use-iov_offset-for-length-calculation-in-iov_iter_aligned_bvec.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/iov_iter-use-iov_offset-for-length-calculation-in-iov_iter_aligned_bvec.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Nitesh Shetty <nj.shetty@samsung.com>
Subject: iov_iter: use iov_offset for length calculation in iov_iter_aligned_bvec
Date: Mon, 28 Apr 2025 15:28:48 +0530

If iov_offset is non-zero, then we need to consider iov_offset in length
calculation, otherwise we might pass smaller IOs such as 512 bytes, in
below scenario [1].

This issue is reproducible using lib-uring test/fixed-seg.c application
with fixed buffer on a 512 LBA formatted device.

[1]
At present we pass the alignment check,
for 512 LBA formatted devices, len_mask = 511
when IO is smaller, i->count = 512
has an offset, i->io_offset = 3584
with bvec values, bvec->bv_offset = 256, bvec->bv_len = 3840.
In short, the first 256 bytes are in the current page,
next 256 bytes are in the another page.
Ideally we expect to fail the IO.

Link: https://lkml.kernel.org/r/20250428095849.11709-1-nj.shetty@samsung.com
Fixes: 2263639f96f2 ("iov_iter: streamline iovec/bvec alignment iteration")
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Reviewed-by: Anuj Gupta <anuj20.g@samsung.com>
Signed-off-by: Nitesh Shetty <nj.shetty@samsung.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Keith Busch <kbusch@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 lib/iov_iter.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/lib/iov_iter.c~iov_iter-use-iov_offset-for-length-calculation-in-iov_iter_aligned_bvec
+++ a/lib/iov_iter.c
@@ -820,7 +820,7 @@ static bool iov_iter_aligned_bvec(const
 	size_t size = i->count;
 
 	do {
-		size_t len = bvec->bv_len;
+		size_t len = bvec->bv_len - skip;
 
 		if (len > size)
 			len = size;
_

Patches currently in -mm which might be from nj.shetty@samsung.com are

iov_iter-use-iov_offset-for-length-calculation-in-iov_iter_aligned_bvec.patch