6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: OGAWA Hirofumi [ Upstream commit 63c4b67ee163b2a67a7561314bf2106d6c79c53c ] commit 64d9183203ee ("fat: restore original value when fat_ent_write failed") try to revert the fatent value to old value when got the error on mirror FAT. However it didn't work if the error is when writing the fatent bh. In that case, the bh is cleared the uptodate flag, so reuse bh is invalid. Fix this by reverting the fatent only if got the error on mirror FAT. Link: https://lore.kernel.org/87ik4yz9fv.fsf_-_@mail.parknet.co.jp Fixes: 64d9183203ee ("fat: restore original value when fat_ent_write failed") Signed-off-by: OGAWA Hirofumi Signed-off-by: Andrew Morton Reported-by: syzbot+e64c6472a3d96a75172a@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=e64c6472a3d96a75172a Reported-by: syzbot+26461e903494e689c24f@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=26461e903494e689c24f Cc: Yemu Lu Cc: Ren Wei Cc: Yuan Tan Cc: Yifan Wu Cc: Juefei Pu Cc: Xin Liu Cc: Signed-off-by: Sasha Levin --- fs/fat/fat.h | 2 +- fs/fat/fatent.c | 21 ++++++++++++++++++--- fs/fat/file.c | 3 ++- fs/fat/misc.c | 6 ++---- 4 files changed, 23 insertions(+), 9 deletions(-) diff --git a/fs/fat/fat.h b/fs/fat/fat.h index d3e426de5f016..6748dea6cd216 100644 --- a/fs/fat/fat.h +++ b/fs/fat/fat.h @@ -389,7 +389,7 @@ extern void fat_ent_access_init(struct super_block *sb); extern int fat_ent_read(struct inode *inode, struct fat_entry *fatent, int entry); extern int fat_ent_write(struct inode *inode, struct fat_entry *fatent, - int new, int wait); + int new, int old, int wait); extern int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster); extern int fat_free_clusters(struct inode *inode, int cluster); diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c index a7061c2ad8e4d..515bc0cfc64f1 100644 --- a/fs/fat/fatent.c +++ b/fs/fat/fatent.c @@ -408,7 +408,7 @@ static int fat_mirror_bhs(struct super_block *sb, struct buffer_head **bhs, } int fat_ent_write(struct inode *inode, struct fat_entry *fatent, - int new, int wait) + int new, int old, int wait) { struct super_block *sb = inode->i_sb; const struct fatent_operations *ops = MSDOS_SB(sb)->fatent_ops; @@ -417,10 +417,25 @@ int fat_ent_write(struct inode *inode, struct fat_entry *fatent, ops->ent_put(fatent, new); if (wait) { err = fat_sync_bhs(fatent->bhs, fatent->nr_bhs); - if (err) + if (err) { + /* + * bhs are not uptodate after I/O error. So we + * can't simply re-dirty to revert. And it + * would not have value to write again on I/O + * error. + */ return err; + } } - return fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs); + + err = fat_mirror_bhs(sb, fatent->bhs, fatent->nr_bhs); + if (err) { + /* Try to revert if got the error on mirror FAT */ + ops->ent_put(fatent, old); + if (wait) + fat_sync_bhs(fatent->bhs, fatent->nr_bhs); + } + return err; } static inline int fat_ent_next(struct msdos_sb_info *sbi, diff --git a/fs/fat/file.c b/fs/fat/file.c index 4fc49a614fb8f..ca2f9db34da5c 100644 --- a/fs/fat/file.c +++ b/fs/fat/file.c @@ -360,7 +360,8 @@ static int fat_free(struct inode *inode, int skip) __func__, MSDOS_I(inode)->i_pos); ret = -EIO; } else if (ret > 0) { - err = fat_ent_write(inode, &fatent, FAT_ENT_EOF, wait); + err = fat_ent_write(inode, &fatent, FAT_ENT_EOF, ret, + wait); if (err) ret = err; } diff --git a/fs/fat/misc.c b/fs/fat/misc.c index 5c45603bf77ea..c0bc4356eded3 100644 --- a/fs/fat/misc.c +++ b/fs/fat/misc.c @@ -133,11 +133,9 @@ int fat_chain_add(struct inode *inode, int new_dclus, int nr_cluster) ret = fat_ent_read(inode, &fatent, last); if (ret >= 0) { int wait = inode_needs_sync(inode); - int old = ret; - ret = fat_ent_write(inode, &fatent, new_dclus, wait); - if (ret < 0) - fat_ent_write(inode, &fatent, old, wait); + ret = fat_ent_write(inode, &fatent, new_dclus, ret, + wait); fatent_brelse(&fatent); } if (ret < 0) -- 2.53.0