From: Matthew Wilcox <willy@infradead.org>
To: Naman Jain <namjain@linux.microsoft.com>
Cc: Theodore Ts'o <tytso@mit.edu>,
Andreas Dilger <adilger.kernel@dilger.ca>,
Sasha Levin <sashal@kernel.org>,
stable@vger.kernel.org, linux-ext4@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 6.1] ext4: honor NULL returns from __filemap_get_folio()
Date: Mon, 2 Nov 2026 17:09:15 +0000 [thread overview]
Message-ID: <aujDuxgeH-TyEsXh@casper.infradead.org> (raw)
In-Reply-To: <20261102163341.2170232-1-namjain@linux.microsoft.com>
On Mon, Nov 02, 2026 at 04:33:41PM +0000, Naman Jain wrote:
> The bitmap and buddy folio conversions assume that
> __filemap_get_folio() returns error pointers. In Linux 6.1, however,
> it returns NULL both when a non-creating lookup misses and when folio
> creation fails.
>
> A cache miss therefore passes the IS_ERR() check and reaches
> folio_test_uptodate(NULL) in ext4_mb_load_buddy_gfp(). Creating-lookup
> failures can also dereference NULL in its slow paths and in
> ext4_mb_get_buddy_page_lock().
>
> Restore NULL checks at all six lookup sites and return -ENOMEM when a
> creating lookup fails. Preserve the folio locking and migration checks
> without changing the global filemap API.
>
> Fixes: d34e4fd4e73f ("ext4: convert bd_bitmap_page to bd_bitmap_folio")
> Fixes: 862483175d3d ("ext4: convert bd_buddy_page to bd_buddy_folio")
> Cc: stable@vger.kernel.org # 6.1.x
> Signed-off-by: Naman Jain <namjain@linux.microsoft.com>
Elliot beat you to it:
https://lore.kernel.org/linux-ext4/20261102-ext4-ntfs3-null-folio-v1-0-4fd91ee23a4a@elliotjb.com/
Care to drop a R-b on his series?
next prev parent reply other threads:[~2026-11-02 17:09 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-11-02 16:33 Naman Jain
2026-11-02 17:09 ` Matthew Wilcox [this message]
2026-11-02 17:24 ` Naman Jain
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