Messages in this thread Patch in this message | | | Date | Mon, 18 Jun 2012 16:31:31 +0900 (JST) | Subject | [PATCH] Fixing double brelse'ing bh allocated in gfs2_meta_read when EIO occurs | From | Masatake YAMATO <> |
| |
This patch fixes buffer_head double free in following code path:
gfs2_block_map => gfs2_meta_inode_buffer => gfs2_meta_indirect_buffer => gfs2_meta_read => release_metapath
gfs2_block_map calls gfs2_meta_inode_buffer with &mp.mp_bh[0] as an argument. mp.mp_bh are filled with zero at the beginning of gfs2_block_map.
If gfs2_meta_inode_buffer returns non-zero value, gfs2_block_map calls release_metapath to free buffers chained to mp.mp_bh. release_metapath checks each slot of mp.mp_bh[i] and free(with brelse) unless the slot is filled with NULL.
&mp.mp_bh[0] passed to gfs2_meta_inode_buffer is filled at gfs2_meta_read. gfs2_meta_read is filled a buffer allocated with gfs2_getbuf even if EIO occurs. When EIO occurs, the allocated buffer is brelse'ed though the pointer(wrong poiner) points the brelse'ed is passed back to caller via an argument bhp.
gfs2_meta_indirect_buffer, the caller also pass the wrong pointer to its caller with EIO. Finally gfs2_block_map gets both EIO and &mp.mp_bh[0] filled with the wrong pointer. release_metapath calls brelse again on the wrong pointer.
Signed-off-by: Masatake YAMATO<yamato@redhat.com>
diff --git a/fs/gfs2/meta_io.c b/fs/gfs2/meta_io.c index 6c1e5d1..3a56c8d 100644 --- a/fs/gfs2/meta_io.c +++ b/fs/gfs2/meta_io.c @@ -213,8 +213,10 @@ int gfs2_meta_read(struct gfs2_glock *gl, u64 blkno, int flags, struct gfs2_sbd *sdp = gl->gl_sbd; struct buffer_head *bh; - if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags))) + if (unlikely(test_bit(SDF_SHUTDOWN, &sdp->sd_flags))) { + *bhp = NULL; return -EIO; + } *bhp = bh = gfs2_getbuf(gl, blkno, CREATE); @@ -235,6 +237,7 @@ int gfs2_meta_read(struct gfs2_glock *gl, u64 blkno, int flags, if (tr && tr->tr_touched) gfs2_io_error_bh(sdp, bh); brelse(bh); + *bhp = NULL; return -EIO; }
| |