| Message ID | 1482994539-48559-1-git-send-email-yi.zhang@huawei.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Thu 29-12-16 14:55:39, yi zhang wrote: > Because of the disk and hardware issue, the ext4 filesystem have > many errors, the inode->i_nlink of ext4 becomes zero abnormally > but the dentry is still positive, it will cause memory corruption > after the following process: > > 1) Due to the inode->i_nlink is 0, this inode will be added into > the orhpan list, > 2) ext4_rename() cover this inode, and drop_nlink() will reverse > the inode->i_nlink to 0xFFFFFFFF, > 3) iput() add this inode to LRU, > 4) evict() will call destroy_inode() to destroy this inode but > skip removing it from the orphan list, > 5) after this, the inode's memory address space will be used by > other module, when the ext4 filesystem change the orphan list, it will > trample other module's data and then may cause oops. > > Although we cannot avoid hardware and disk errors, we can control the > softwore error in the ext4 module, do not affect other modules and > increase the difficulty of locating problems. > > This patch avoid inode->i_nlink reverse and remove the inode from the > orphan list when destroy it if the list is not empty. > > changes since: v1 > - correct a spelling mistake. > - change the style of the WARN string. > > Signed-off-by: yi zhang <yi.zhang@huawei.com> The patch looks good to me. You can add: Reviewed-by: Jan Kara <jack@suse.cz> Honza > --- > fs/ext4/super.c | 1 + > fs/inode.c | 5 ++++- > 2 files changed, 5 insertions(+), 1 deletion(-) > > diff --git a/fs/ext4/super.c b/fs/ext4/super.c > index 52b0530..617327e 100644 > --- a/fs/ext4/super.c > +++ b/fs/ext4/super.c > @@ -975,6 +975,7 @@ static void ext4_destroy_inode(struct inode *inode) > EXT4_I(inode), sizeof(struct ext4_inode_info), > true); > dump_stack(); > + ext4_orphan_del(NULL, inode); > } > call_rcu(&inode->i_rcu, ext4_i_callback); > } > diff --git a/fs/inode.c b/fs/inode.c > index 88110fd..079d383 100644 > --- a/fs/inode.c > +++ b/fs/inode.c > @@ -279,7 +279,10 @@ static void destroy_inode(struct inode *inode) > */ > void drop_nlink(struct inode *inode) > { > - WARN_ON(inode->i_nlink == 0); > + if (WARN(inode->i_nlink == 0, > + "inode %lu nlink is already 0", inode->i_ino)) > + return; > + > inode->__i_nlink--; > if (!inode->i_nlink) > atomic_long_inc(&inode->i_sb->s_remove_count); > -- > 2.5.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/fs/ext4/super.c b/fs/ext4/super.c index 52b0530..617327e 100644 --- a/fs/ext4/super.c +++ b/fs/ext4/super.c @@ -975,6 +975,7 @@ static void ext4_destroy_inode(struct inode *inode) EXT4_I(inode), sizeof(struct ext4_inode_info), true); dump_stack(); + ext4_orphan_del(NULL, inode); } call_rcu(&inode->i_rcu, ext4_i_callback); } diff --git a/fs/inode.c b/fs/inode.c index 88110fd..079d383 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -279,7 +279,10 @@ static void destroy_inode(struct inode *inode) */ void drop_nlink(struct inode *inode) { - WARN_ON(inode->i_nlink == 0); + if (WARN(inode->i_nlink == 0, + "inode %lu nlink is already 0", inode->i_ino)) + return; + inode->__i_nlink--; if (!inode->i_nlink) atomic_long_inc(&inode->i_sb->s_remove_count);
Because of the disk and hardware issue, the ext4 filesystem have many errors, the inode->i_nlink of ext4 becomes zero abnormally but the dentry is still positive, it will cause memory corruption after the following process: 1) Due to the inode->i_nlink is 0, this inode will be added into the orhpan list, 2) ext4_rename() cover this inode, and drop_nlink() will reverse the inode->i_nlink to 0xFFFFFFFF, 3) iput() add this inode to LRU, 4) evict() will call destroy_inode() to destroy this inode but skip removing it from the orphan list, 5) after this, the inode's memory address space will be used by other module, when the ext4 filesystem change the orphan list, it will trample other module's data and then may cause oops. Although we cannot avoid hardware and disk errors, we can control the softwore error in the ext4 module, do not affect other modules and increase the difficulty of locating problems. This patch avoid inode->i_nlink reverse and remove the inode from the orphan list when destroy it if the list is not empty. changes since: v1 - correct a spelling mistake. - change the style of the WARN string. Signed-off-by: yi zhang <yi.zhang@huawei.com> --- fs/ext4/super.c | 1 + fs/inode.c | 5 ++++- 2 files changed, 5 insertions(+), 1 deletion(-)