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Tue, 13 Oct 2026 04:57:35 -0700 (PDT) From: Nanzhe Zhao To: linux-f2fs-devel@lists.sourceforge.net, Jaegeuk Kim , Chao Yu Cc: Barry Song , Nanzhe Zhao , Juan Yescas , Daeho Jeong , Dev Jain , David Hildenbrand , linux-kernel@vger.kernel.org, Bo Zhang , Kalesh Singh , Nanzhe Zhao , Pengfei Li , Ryan Roberts , kernel test robot Subject: [PATCH v4 14/18] f2fs: wait for folio writeback before ffs_detach_free Date: Tue, 13 Oct 2026 19:56:17 +0800 Message-ID: <20261013115621.968742-15-nzzhao.sigma@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20261013115621.968742-1-nzzhao.sigma@gmail.com> References: <20261013115621.968742-1-nzzhao.sigma@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Nanzhe Zhao truncate_inode_pages_range() can invalidate a large folio that is still under writeback, which can result in the following use-after-free: CPU0 (writeback) CPU1 (truncate) ---- ---- f2fs_write_cache_folios() folio_start_writeback(folio) /* submit bios */ retry_out: folio_unlock(folio) /* all bios submitted; folio lock released */ truncate_inode_pages_range() find_lock_entries() /* locks the folio */ truncate_cleanup_folio(folio) folio_invalidate(folio, 0, folio_size(folio)) -> f2fs_invalidate_folio(folio, 0, folio_size(folio)) f2fs_write_end_bio(bio) ffs = folio->private ffs_detach_free(folio) folio_detach_private(folio) kfree(ffs) atomic_sub_and_test(nr_pages, &ffs->write_pages_pending) <-- use-after-free Wait for folio writeback in invalidate_folio, then we can free the folio state without any other remaining user. Reported-by: kernel test robot Closes: https://lore.kernel.org/oe-lkp/202610081027.b13dcf10-lkp@intel.com Signed-off-by: Nanzhe Zhao --- fs/f2fs/data.c | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/fs/f2fs/data.c b/fs/f2fs/data.c index 61fe4a0c5..433d8f2b0 100644 --- a/fs/f2fs/data.c +++ b/fs/f2fs/data.c @@ -5427,6 +5427,14 @@ void f2fs_invalidate_folio(struct folio *folio, size_t offset, size_t length) } if (f2fs_folio_has_ffs(folio)) { + /* + * The folio may still be under writeback with bios in + * completion that need to access f2fs_folio_state. Wait + * for the writeback to complete before freeing the state, + * otherwise it will result in use-after-free. + */ + folio_wait_writeback(folio); + f2fs_ffs_clear_subrange_dirty_and_test(folio, 0, folio_size(folio)); } else if (folio_test_dirty(folio)) { -- 2.43.0