From 8bafd6054e09fd2c866bf0d031855eafd29fc200 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Sat, 23 Aug 2014 17:47:28 -0400 Subject: [PATCH] ext4: fix BUG_ON in mb_free_blocks() commit c99d1e6e83b06744c75d9f5e491ed495a7086b7b upstream. If we suffer a block allocation failure (for example due to a memory allocation failure), it's possible that we will call ext4_discard_allocated_blocks() before we've actually allocated any blocks. In that case, fe_len and fe_start in ac->ac_f_ex will still be zero, and this will result in mb_free_blocks(inode, e4b, 0, 0) triggering the BUG_ON on mb_free_blocks(): BUG_ON(last >= (sb->s_blocksize << 3)); Fix this by bailing out of ext4_discard_allocated_blocks() if fs_len is zero. Also fix a missing ext4_mb_unload_buddy() call in ext4_discard_allocated_blocks(). Google-Bug-Id: 16844242 Fixes: 86f0afd463215fc3e58020493482faa4ac3a4d69 Signed-off-by: Theodore Ts'o Signed-off-by: Greg Kroah-Hartman --- fs/ext4/mballoc.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c index 795d5af..242226a 100644 --- a/fs/ext4/mballoc.c +++ b/fs/ext4/mballoc.c @@ -1398,6 +1398,8 @@ static void mb_free_blocks(struct inode *inode, struct ext4_buddy *e4b, int last = first + count - 1; struct super_block *sb = e4b->bd_sb; + if (WARN_ON(count == 0)) + return; BUG_ON(last >= (sb->s_blocksize << 3)); assert_spin_locked(ext4_group_lock_ptr(sb, e4b->bd_group)); /* Don't bother if the block group is corrupt. */ @@ -3200,6 +3202,8 @@ static void ext4_discard_allocated_blocks(struct ext4_allocation_context *ac) int err; if (pa == NULL) { + if (ac->ac_f_ex.fe_len == 0) + return; err = ext4_mb_load_buddy(ac->ac_sb, ac->ac_f_ex.fe_group, &e4b); if (err) { /* @@ -3214,6 +3218,7 @@ static void ext4_discard_allocated_blocks(struct ext4_allocation_context *ac) mb_free_blocks(ac->ac_inode, &e4b, ac->ac_f_ex.fe_start, ac->ac_f_ex.fe_len); ext4_unlock_group(ac->ac_sb, ac->ac_f_ex.fe_group); + ext4_mb_unload_buddy(&e4b); return; } if (pa->pa_type == MB_INODE_PA) -- 2.7.4