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Thu, 02 Jul 2026 20:39:18 -0700 (PDT) From: =?UTF-8?q?=EC=9D=B4=EC=83=81=ED=98=B8?= To: Namjae Jeon Cc: Sangho Lee , Hyunchul Lee , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [BUG/RFC] ntfs: crafted image triggers WARN_ON in ntfs_map_runlist_nolock() Date: Fri, 3 Jul 2026 12:39:14 +0900 Message-ID: <20260703033914.98698-1-kudo3228@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: <20260701221237.822167-1-kudo3228@gmail.com> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit From: Sangho Lee Hi Namjae, Thanks for the patch. I applied it to my NTFS test tree and rebuilt the kernel. I then reran syz-repro with the same syzkaller crash log that reproduced the original WARN_ON in ntfs_map_runlist_nolock() on the unpatched kernel. Result: - unpatched kernel: the same log reproduced the WARN_ON in ntfs_map_runlist_nolock() - patched kernel: syz-repro ran through all extraction phases for 29m28s and failed to reproduce the warning: - 15s single runs: no crash - 15s grouped/bisect: did not crash - 1m40s single runs: no crash - 1m55s grouped/bisect: did not crash - 6m single runs: no crash - 6m15s grouped/bisect: did not crash - no kernel WARNING/Oops/BUG lines were observed The change also matches the root cause I saw: when ctx_needs_reset is true, ntfs_map_runlist_nolock() can reach the runlist mapping path for a resident attribute. Returning -EIO before using the non-resident mapping fields avoids triggering the WARN_ON and prevents the invalid path. So yes, this patch fixes the issue from my side. Tested-by: Sangho Lee Thanks, Sangho