From ad4497a92caba4630f75c80d49cb947026213280 Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Tue, 8 Sep 2026 23:06:08 -0700 Subject: [PATCH] xfs: advance the findparent inode scan cursor while holding ILOCK LOLLM pointed out a race condition in xrep_findparent_scan -- the directory live update hook holds the directory ILOCK when it calls the xchk_iscan_want_live_update predicate to figure out if it needs to remember the live update, but xrep_findparent_scan drops the directory ILOCK before advancing the cursor. Therefore, it's possible for a live update to check the scan cursor after the scan drops the ILOCK but before the scan updates its cursor. If this happens, we'll fail to record the live update. Fix this by moving the cursor update logic inside xrep_findparent_walk_directory. Note that for non-directories it's ok to advance the cursor without holding any ILOCK because the findparent scan only cares about directory parents, not the children. Cc: stable@vger.kernel.org # v6.10 Fixes: a07b45576264e7 ("xfs: scan the filesystem to repair a directory dotdot entry") Signed-off-by: Darrick J. Wong Assisted-by: LOLLM # finding obvious bugs Reviewed-by: Carlos Maiolino Reviewed-by: Christoph Hellwig Signed-off-by: Carlos Maiolino --- fs/xfs/scrub/findparent.c | 56 ++++++++++++++++++++++++++------------- 1 file changed, 37 insertions(+), 19 deletions(-) diff --git a/fs/xfs/scrub/findparent.c b/fs/xfs/scrub/findparent.c index 04b6b96b0a30..eab3ac2704be 100644 --- a/fs/xfs/scrub/findparent.c +++ b/fs/xfs/scrub/findparent.c @@ -139,12 +139,40 @@ xrep_findparent_dirent( return 0; } +static inline bool +xrep_findparent_want_scan_file( + const struct xrep_findparent_info *fpi) +{ + const struct xfs_scrub *sc = fpi->sc; + const struct xfs_inode *dp = fpi->dp; + + /* Only directories can be parents */ + if (!S_ISDIR(VFS_IC(dp)->i_mode)) + return false; + + /* + * The inode being scanned cannot be its own parent, nor can any + * temporary directory we created to stage this repair. + */ + if (dp == sc->ip || dp == sc->tempip) + return false; + + /* + * Similarly, temporary files created to stage a repair cannot be the + * parent of this inode. + */ + if (xrep_is_tempfile(dp)) + return false; + + return true; +} + /* * If this is a directory, walk the dirents looking for any that point to the * scrub target inode. */ STATIC int -xrep_findparent_walk_directory( +xrep_findparent_walk_file( struct xrep_findparent_info *fpi) { struct xfs_scrub *sc = fpi->sc; @@ -152,19 +180,11 @@ xrep_findparent_walk_directory( unsigned int lock_mode; int error = 0; - /* - * The inode being scanned cannot be its own parent, nor can any - * temporary directory we created to stage this repair. - */ - if (dp == sc->ip || dp == sc->tempip) - return 0; - - /* - * Similarly, temporary files created to stage a repair cannot be the - * parent of this inode. - */ - if (xrep_is_tempfile(dp)) + if (!xrep_findparent_want_scan_file(fpi)) { + if (fpi->parent_scan) + xchk_iscan_mark_visited(&fpi->parent_scan->iscan, dp); return 0; + } /* * Scan the directory to see if there it contains an entry pointing to @@ -201,6 +221,8 @@ xrep_findparent_walk_directory( goto out_unlock; out_unlock: + if (fpi->parent_scan) + xchk_iscan_mark_visited(&fpi->parent_scan->iscan, dp); xfs_iunlock(dp, lock_mode); return error; } @@ -308,11 +330,7 @@ xrep_findparent_scan( ASSERT(S_ISDIR(VFS_IC(sc->ip)->i_mode)); while ((ret = xchk_iscan_iter(&pscan->iscan, &fpi.dp)) == 1) { - if (S_ISDIR(VFS_I(fpi.dp)->i_mode)) - ret = xrep_findparent_walk_directory(&fpi); - else - ret = 0; - xchk_iscan_mark_visited(&pscan->iscan, fpi.dp); + ret = xrep_findparent_walk_file(&fpi); xchk_irele(sc, fpi.dp); if (ret) break; @@ -401,7 +419,7 @@ xrep_findparent_confirm( goto out_rele; } - error = xrep_findparent_walk_directory(&fpi); + error = xrep_findparent_walk_file(&fpi); if (error) goto out_rele;