The branch main has been updated by delphij: URL: https://cgit.FreeBSD.org/src/commit/?id=6cf0d6c3b5777e053074200ff99dc4b750e62b96
commit 6cf0d6c3b5777e053074200ff99dc4b750e62b96 Author: Jie Li <[email protected]> AuthorDate: 2026-09-02 06:15:05 +0000 Commit: Xin LI <[email protected]> CommitDate: 2026-09-03 02:16:10 +0000 fsck_msdosfs: fix status accounting for lost cluster chains checklost() scans for lost cluster chains and attempts to repair each one, first by reconnecting it to LOST.DIR, and falling back to clearing it if reconnection fails. However, checklost() incorrectly updates the modification status flags (mod), which checkfilesys() relies on to determine whether to write back changes and what exit status to return. The current code have three issues: 1. A reconnect() failure immediately sets FSERROR in mod via "mod |= ret = reconnect(...)". If reconnect() failed (e.g., because LOST.DIR is missing, or full) but the fallback clear operation succeeds, clearchain() frees the chain and sets FSFATMOD. However, the leftover FSERROR remains in mod: checkfilesys() skips marking the file system clean and exits with status 8, even though the file system was fully repaired and a subsequent run finds nothing left to do. This can happen with "fsck_msdosfs -y" on a volume without LOST.DIR. 2. The same assignment overwrites checkchain()'s return value before it can be recorded in mod. When checkchain() truncates a chain (e.g., one whose tail points to a free cluster), its FSFATMOD status is lost, causing checkfilesys() to skip updating the FAT and discard the truncation. With LOST.DIR present so that reconnect() succeeds, "fsck_msdosfs -y" reports "Truncate? yes" and "FILE SYSTEM WAS MODIFIED", exits 0, but leaves the identical damage on disk to be found again on every subsequent run. Similarly, an FSFATAL return value from checkchain() is dropped, defeating the "if (mod & FSFATAL) break" guard that follows. 3. When checkchain() returns FSERROR and clearing the chain is declined, no error status is recorded in mod, causing fsck_msdosfs to report a clean exit despite leaving un-repaired damage. Fix these issues by: - Merge checkchain()'s status into mod before calling reconnect(), and skip reconnect() if checkchain() returned a fatal error. - Defer recording FSERROR from a failed reconnect() until after the Clear fallback attempt, setting FSERROR only if the chain remains unhandled. MFC after: 1 week Pull Request: https://github.com/freebsd/freebsd-src/pull/2251 --- sbin/fsck_msdosfs/fat.c | 41 ++++++++++++++++++++++++++++++++--------- 1 file changed, 32 insertions(+), 9 deletions(-) diff --git a/sbin/fsck_msdosfs/fat.c b/sbin/fsck_msdosfs/fat.c index 5ead0b1bf783..d71ac2b503f5 100644 --- a/sbin/fsck_msdosfs/fat.c +++ b/sbin/fsck_msdosfs/fat.c @@ -1284,18 +1284,41 @@ checklost(struct fat_descriptor *fat) } if (fat_is_cl_head(fat, head)) { ret = checkchain(fat, head, &chainlength); - if (ret != FSERROR && chainlength > 0) { - pwarn("Lost cluster chain at cluster %u\n" - "%zd Cluster(s) lost\n", - head, chainlength); - mod |= ret = reconnect(fat, head, - chainlength); + /* + * Record whether checkchain() has repaired the + * chain (FSFATMOD) or died trying (FSFATAL) before + * reconnect() overwrites ret, otherwise the repair + * is never written back. + */ + if (ret != FSERROR) { + mod |= ret; + if (!(mod & FSFATAL) && chainlength > 0) { + pwarn( + "Lost cluster chain at cluster %u\n" + "%zd Cluster(s) lost\n", + head, chainlength); + ret = reconnect(fat, head, chainlength); + if (ret != FSERROR) + mod |= ret; + } } if (mod & FSFATAL) break; - if (ret == FSERROR && ask(0, "Clear")) { - clearchain(fat, head); - mod |= FSFATMOD; + /* + * If reconnect() failed (or checkchain() truncation + * was declined), defer folding FSERROR into mod until + * the Clear fallback is known: if the lost chain is + * cleared, the error has been resolved and must not + * report an exit code 8; otherwise record FSERROR as + * an unrecovered error. + */ + if (ret == FSERROR) { + if (ask(0, "Clear")) { + clearchain(fat, head); + mod |= FSFATMOD; + } else { + mod |= FSERROR; + } } chains--; }
