udf: fix possible leakage of blocks

We have to take care that when we call udf_discard_prealloc() from
udf_clear_inode() we have to write inode ourselves afterwards (otherwise,
some changes might be lost leading to leakage of blocks, use of free blocks
or improperly aligned extents).

Also udf_discard_prealloc() does two different things - it removes
preallocated blocks and truncates the last extent to exactly match i_size.
We move the latter functionality to udf_truncate_tail_extent(), call
udf_discard_prealloc() when last reference to a file is dropped and call
udf_truncate_tail_extent() when inode is being removed from inode cache
(udf_clear_inode() call).

We cannot call udf_truncate_tail_extent() earlier as subsequent open+write
would find the last block of the file mapped and happily write to the end
of it, although the last extent says it's shorter.

[akpm@linux-foundation.org: Make checkpatch.pl happier]
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: Eric Sandeen <sandeen@sandeen.net>
Cc: Cyrill Gorcunov <gorcunov@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

3 files changed, 74 insertions, 17 deletions

diff --git a/fs/udf/inode.c b/fs/udf/inode.c
index 1f0129405cf4..bf7de0bdbab3 100644
--- a/fs/udf/inode.c
+++ b/fs/udf/inode.c
@@ -100,14 +100,23 @@ no_delete:
         clear_inode(inode);
 }
 
+/*
+ * If we are going to release inode from memory, we discard preallocation and
+ * truncate last inode extent to proper length. We could use drop_inode() but
+ * it's called under inode_lock and thus we cannot mark inode dirty there.  We
+ * use clear_inode() but we have to make sure to write inode as it's not written
+ * automatically.
+ */
 void udf_clear_inode(struct inode *inode)
 {
         if (!(inode->i_sb->s_flags & MS_RDONLY)) {
                 lock_kernel();
+                /* Discard preallocation for directories, symlinks, etc. */
                 udf_discard_prealloc(inode);
+                udf_truncate_tail_extent(inode);
                 unlock_kernel();
+                write_inode_now(inode, 1);
         }
-
         kfree(UDF_I_DATA(inode));
         UDF_I_DATA(inode) = NULL;
 }
diff --git a/fs/udf/truncate.c b/fs/udf/truncate.c
index 77975ae291a5..60d277644248 100644
--- a/fs/udf/truncate.c
+++ b/fs/udf/truncate.c
@@ -61,7 +61,11 @@ static void extent_trunc(struct inode * inode, struct extent_position *epos,
         }
 }
 
-void udf_discard_prealloc(struct inode * inode)
+/*
+ * Truncate the last extent to match i_size. This function assumes
+ * that preallocation extent is already truncated.
+ */
+void udf_truncate_tail_extent(struct inode *inode)
 {
         struct extent_position epos = { NULL, 0, {0, 0}};
         kernel_lb_addr eloc;
@@ -71,7 +75,10 @@ void udf_discard_prealloc(struct inode * inode)
         int adsize;
 
         if (UDF_I_ALLOCTYPE(inode) == ICBTAG_FLAG_AD_IN_ICB ||
-                inode->i_size == UDF_I_LENEXTENTS(inode))
+            inode->i_size == UDF_I_LENEXTENTS(inode))
+                return;
+        /* Are we going to delete the file anyway? */
+        if (inode->i_nlink == 0)
                 return;
 
         if (UDF_I_ALLOCTYPE(inode) == ICBTAG_FLAG_AD_SHORT)
@@ -79,36 +86,76 @@ void udf_discard_prealloc(struct inode * inode)
         else if (UDF_I_ALLOCTYPE(inode) == ICBTAG_FLAG_AD_LONG)
                 adsize = sizeof(long_ad);
         else
-                adsize = 0;
-
-        epos.block = UDF_I_LOCATION(inode);
+                BUG();
 
         /* Find the last extent in the file */
         while ((netype = udf_next_aext(inode, &epos, &eloc, &elen, 1)) != -1)
         {
                 etype = netype;
                 lbcount += elen;
-                if (lbcount > inode->i_size && lbcount - elen < inode->i_size)
-                {
-                        WARN_ON(lbcount - inode->i_size >= inode->i_sb->s_blocksize);
+                if (lbcount > inode->i_size) {
+                        if (lbcount - inode->i_size >= inode->i_sb->s_blocksize)
+                                printk(KERN_WARNING
+                                       "udf_truncate_tail_extent(): Too long "
+                                       "extent after EOF in inode %u: i_size: "
+                                       "%Ld lbcount: %Ld extent %u+%u\n",
+                                       (unsigned)inode->i_ino,
+                                       (long long)inode->i_size,
+                                       (long long)lbcount,
+                                       (unsigned)eloc.logicalBlockNum,
+                                       (unsigned)elen);
                         nelen = elen - (lbcount - inode->i_size);
                         epos.offset -= adsize;
                         extent_trunc(inode, &epos, eloc, etype, elen, nelen);
                         epos.offset += adsize;
-                        lbcount = inode->i_size;
+                        if (udf_next_aext(inode, &epos, &eloc, &elen, 1) != -1)
+                                printk(KERN_ERR "udf_truncate_tail_extent(): "
+                                       "Extent after EOF in inode %u.\n",
+                                       (unsigned)inode->i_ino);
+                        break;
                 }
         }
+        /* This inode entry is in-memory only and thus we don't have to mark
+         * the inode dirty */
+        UDF_I_LENEXTENTS(inode) = inode->i_size;
+        brelse(epos.bh);
+}
+
+void udf_discard_prealloc(struct inode *inode)
+{
+        struct extent_position epos = { NULL, 0, {0, 0}};
+        kernel_lb_addr eloc;
+        uint32_t elen;
+        uint64_t lbcount = 0;
+        int8_t etype = -1, netype;
+        int adsize;
+
+        if (UDF_I_ALLOCTYPE(inode) == ICBTAG_FLAG_AD_IN_ICB ||
+                inode->i_size == UDF_I_LENEXTENTS(inode))
+                return;
+
+        if (UDF_I_ALLOCTYPE(inode) == ICBTAG_FLAG_AD_SHORT)
+                adsize = sizeof(short_ad);
+        else if (UDF_I_ALLOCTYPE(inode) == ICBTAG_FLAG_AD_LONG)
+                adsize = sizeof(long_ad);
+        else
+                adsize = 0;
+
+        epos.block = UDF_I_LOCATION(inode);
+
+        /* Find the last extent in the file */
+        while ((netype = udf_next_aext(inode, &epos, &eloc, &elen, 1)) != -1) {
+                etype = netype;
+                lbcount += elen;
+        }
         if (etype == (EXT_NOT_RECORDED_ALLOCATED >> 30)) {
                 epos.offset -= adsize;
                 lbcount -= elen;
                 extent_trunc(inode, &epos, eloc, etype, elen, 0);
-                if (!epos.bh)
-                {
+                if (!epos.bh) {
                         UDF_I_LENALLOC(inode) = epos.offset - udf_file_entry_alloc_offset(inode);
                         mark_inode_dirty(inode);
-                }
-                else
-                {
+                } else {
                         struct allocExtDesc *aed = (struct allocExtDesc *)(epos.bh->b_data);
                         aed->lengthAllocDescs = cpu_to_le32(epos.offset - sizeof(struct allocExtDesc));
                         if (!UDF_QUERY_FLAG(inode->i_sb, UDF_FLAG_STRICT) || UDF_SB_UDFREV(inode->i_sb) >= 0x0201)
@@ -118,9 +165,9 @@ void udf_discard_prealloc(struct inode * inode)
                         mark_buffer_dirty_inode(epos.bh, inode);
                 }
         }
+        /* This inode entry is in-memory only and thus we don't have to mark
+         * the inode dirty */
         UDF_I_LENEXTENTS(inode) = lbcount;
-
-        WARN_ON(lbcount != inode->i_size);
         brelse(epos.bh);
 }
 
diff --git a/fs/udf/udfdecl.h b/fs/udf/udfdecl.h
index 67ded289497c..f581f2f69c0f 100644
--- a/fs/udf/udfdecl.h
+++ b/fs/udf/udfdecl.h
@@ -146,6 +146,7 @@ extern void udf_free_inode(struct inode *);
 extern struct inode * udf_new_inode (struct inode *, int, int *);
 
 /* truncate.c */
+extern void udf_truncate_tail_extent(struct inode *);
 extern void udf_discard_prealloc(struct inode *);
 extern void udf_truncate_extents(struct inode *);