gfs2: Fix iomap buffer head reference counting bug

GFS2 passes the inode buffer head (dibh) from gfs2_iomap_begin to
gfs2_iomap_end in iomap->private.  It sets that private pointer in
gfs2_iomap_get.  Users of gfs2_iomap_get other than gfs2_iomap_begin
would have to release iomap->private, but this isn't done correctly,
leading to a leak of buffer head references.

To fix this, move the code for setting iomap->private from
gfs2_iomap_get to gfs2_iomap_begin.

Fixes: 64bc06bb32 ("gfs2: iomap buffered write support")
Cc: stable@vger.kernel.org # v4.19+
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 17 insertions, 23 deletions

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 38d88fcb6988..0d643306c255 100644
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -826,7 +826,7 @@ static int gfs2_iomap_get(struct inode *inode, loff_t pos, loff_t length,
         ret = gfs2_meta_inode_buffer(ip, &dibh);
         if (ret)
                 goto unlock;
-        iomap->private = dibh;
+        mp->mp_bh[0] = dibh;
 
         if (gfs2_is_stuffed(ip)) {
                 if (flags & IOMAP_WRITE) {
@@ -863,9 +863,6 @@ unstuff:
         len = lblock_stop - lblock + 1;
         iomap->length = len << inode->i_blkbits;
 
-        get_bh(dibh);
-        mp->mp_bh[0] = dibh;
-
         height = ip->i_height;
         while ((lblock + 1) * sdp->sd_sb.sb_bsize > sdp->sd_heightsize[height])
                 height++;
@@ -898,8 +895,6 @@ out:
         iomap->bdev = inode->i_sb->s_bdev;
 unlock:
         up_read(&ip->i_rw_mutex);
-        if (ret && dibh)
-                brelse(dibh);
         return ret;
 
 do_alloc:
@@ -980,9 +975,9 @@ static void gfs2_iomap_journaled_page_done(struct inode *inode, loff_t pos,
 
 static int gfs2_iomap_begin_write(struct inode *inode, loff_t pos,
                                   loff_t length, unsigned flags,
-                                  struct iomap *iomap)
+                                  struct iomap *iomap,
+                                  struct metapath *mp)
 {
-        struct metapath mp = { .mp_aheight = 1, };
         struct gfs2_inode *ip = GFS2_I(inode);
         struct gfs2_sbd *sdp = GFS2_SB(inode);
         unsigned int data_blocks = 0, ind_blocks = 0, rblocks;
@@ -996,9 +991,9 @@ static int gfs2_iomap_begin_write(struct inode *inode, loff_t pos,
         unstuff = gfs2_is_stuffed(ip) &&
                   pos + length > gfs2_max_stuffed_size(ip);
 
-        ret = gfs2_iomap_get(inode, pos, length, flags, iomap, &mp);
+        ret = gfs2_iomap_get(inode, pos, length, flags, iomap, mp);
         if (ret)
-                goto out_release;
+                goto out_unlock;
 
         alloc_required = unstuff || iomap->type == IOMAP_HOLE;
 
@@ -1013,7 +1008,7 @@ static int gfs2_iomap_begin_write(struct inode *inode, loff_t pos,
 
                 ret = gfs2_quota_lock_check(ip, &ap);
                 if (ret)
-                        goto out_release;
+                        goto out_unlock;
 
                 ret = gfs2_inplace_reserve(ip, &ap);
                 if (ret)
@@ -1038,17 +1033,15 @@ static int gfs2_iomap_begin_write(struct inode *inode, loff_t pos,
                 ret = gfs2_unstuff_dinode(ip, NULL);
                 if (ret)
                         goto out_trans_end;
-                release_metapath(&mp);
-                brelse(iomap->private);
-                iomap->private = NULL;
+                release_metapath(mp);
                 ret = gfs2_iomap_get(inode, iomap->offset, iomap->length,
-                                     flags, iomap, &mp);
+                                     flags, iomap, mp);
                 if (ret)
                         goto out_trans_end;
         }
 
         if (iomap->type == IOMAP_HOLE) {
-                ret = gfs2_iomap_alloc(inode, iomap, flags, &mp);
+                ret = gfs2_iomap_alloc(inode, iomap, flags, mp);
                 if (ret) {
                         gfs2_trans_end(sdp);
                         gfs2_inplace_release(ip);
@@ -1056,7 +1049,6 @@ static int gfs2_iomap_begin_write(struct inode *inode, loff_t pos,
                         goto out_qunlock;
                 }
         }
-        release_metapath(&mp);
         if (gfs2_is_jdata(ip))
                 iomap->page_done = gfs2_iomap_journaled_page_done;
         return 0;
@@ -1069,10 +1061,7 @@ out_trans_fail:
 out_qunlock:
         if (alloc_required)
                 gfs2_quota_unlock(ip);
-out_release:
-        if (iomap->private)
-                brelse(iomap->private);
-        release_metapath(&mp);
+out_unlock:
         gfs2_write_unlock(inode);
         return ret;
 }
@@ -1088,10 +1077,10 @@ static int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length,
 
         trace_gfs2_iomap_start(ip, pos, length, flags);
         if ((flags & IOMAP_WRITE) && !(flags & IOMAP_DIRECT)) {
-                ret = gfs2_iomap_begin_write(inode, pos, length, flags, iomap);
+                ret = gfs2_iomap_begin_write(inode, pos, length, flags, iomap, &mp);
         } else {
                 ret = gfs2_iomap_get(inode, pos, length, flags, iomap, &mp);
-                release_metapath(&mp);
+
                 /*
                  * Silently fall back to buffered I/O for stuffed files or if
                  * we've hot a hole (see gfs2_file_direct_write).
@@ -1100,6 +1089,11 @@ static int gfs2_iomap_begin(struct inode *inode, loff_t pos, loff_t length,
                     iomap->type != IOMAP_MAPPED)
                         ret = -ENOTBLK;
         }
+        if (!ret) {
+                get_bh(mp.mp_bh[0]);
+                iomap->private = mp.mp_bh[0];
+        }
+        release_metapath(&mp);
         trace_gfs2_iomap_end(ip, iomap, ret);
         return ret;
 }