It's possible to hit a NULL pointer exception while accessing the sb->s_group_info in ext4_validate_inode_bitmap(), when calling ext4_get_group_info(). EXT4-fs (loop0): warning: mounting unchecked fs, running e2fsck is recommended EXT4-fs error (device loop0): ext4_clear_blocks:866: inode #32: comm mount: attempt to clear invalid blocks 16777450 len 1 EXT4-fs error (device loop0): ext4_free_branches:1012: inode #32: comm mount: invalid indirect mapped block 1258291200 (level 1) EXT4-fs error (device loop0): ext4_free_branches:1012: inode #32: comm mount: invalid indirect mapped block 7379847 (level 2) BUG: kernel NULL pointer dereference, address: 0000000000000000 ... RIP: 0010:ext4_read_inode_bitmap+0x21b/0x5a0 ... Call Trace: <TASK> ext4_free_inode+0x172/0x5c0 ext4_evict_inode+0x4a5/0x730 evict+0xc1/0x1c0 ext4_setup_system_zone+0x2ea/0x380 ext4_fill_super+0x249f/0x3910 ? ext4_reconfigure+0x880/0x880 ? snprintf+0x49/0x60 ? ext4_reconfigure+0x880/0x880 get_tree_bdev+0x169/0x260 vfs_get_tree+0x16/0x70 path_mount+0x77d/0xa30 __x64_sys_mount+0x101/0x140 do_syscall_64+0x3c/0x80 entry_SYSCALL_64_after_hwframe+0x46/0xb0 Fix the issue by adding an extra NULL check. And, while there, also ensure the right error code (-EFSCORRUPTED) is propagated to user-space. EUCLEAN is more informative than ENOMEM. CC: stable@xxxxxxxxxxxxxxx Link: https://bugzilla.kernel.org/show_bug.cgi?id=216541 Signed-off-by: Luís Henriques <lhenriques@xxxxxxx> --- fs/ext4/ext4.h | 17 ++++++++++------- fs/ext4/ialloc.c | 2 +- fs/ext4/indirect.c | 14 ++++++++++++-- 3 files changed, 23 insertions(+), 10 deletions(-) diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h index 3bf9a6926798..91317f592999 100644 --- a/fs/ext4/ext4.h +++ b/fs/ext4/ext4.h @@ -3323,13 +3323,16 @@ static inline struct ext4_group_info *ext4_get_group_info(struct super_block *sb, ext4_group_t group) { - struct ext4_group_info **grp_info; - long indexv, indexh; - BUG_ON(group >= EXT4_SB(sb)->s_groups_count); - indexv = group >> (EXT4_DESC_PER_BLOCK_BITS(sb)); - indexh = group & ((EXT4_DESC_PER_BLOCK(sb)) - 1); - grp_info = sbi_array_rcu_deref(EXT4_SB(sb), s_group_info, indexv); - return grp_info[indexh]; + struct ext4_group_info **grp_info; + long indexv, indexh; + + BUG_ON(group >= EXT4_SB(sb)->s_groups_count); + if (!EXT4_SB(sb)->s_group_info) + return NULL; + indexv = group >> (EXT4_DESC_PER_BLOCK_BITS(sb)); + indexh = group & ((EXT4_DESC_PER_BLOCK(sb)) - 1); + grp_info = sbi_array_rcu_deref(EXT4_SB(sb), s_group_info, indexv); + return grp_info[indexh]; } /* diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c index 208b87ce8858..0e8d35d05b69 100644 --- a/fs/ext4/ialloc.c +++ b/fs/ext4/ialloc.c @@ -91,7 +91,7 @@ static int ext4_validate_inode_bitmap(struct super_block *sb, if (buffer_verified(bh)) return 0; - if (EXT4_MB_GRP_IBITMAP_CORRUPT(grp)) + if (!grp || EXT4_MB_GRP_IBITMAP_CORRUPT(grp)) return -EFSCORRUPTED; ext4_lock_group(sb, block_group); diff --git a/fs/ext4/indirect.c b/fs/ext4/indirect.c index 860fc5119009..e5ac5c2363df 100644 --- a/fs/ext4/indirect.c +++ b/fs/ext4/indirect.c @@ -148,6 +148,7 @@ static Indirect *ext4_get_branch(struct inode *inode, int depth, struct super_block *sb = inode->i_sb; Indirect *p = chain; struct buffer_head *bh; + unsigned int key; int ret = -EIO; *err = 0; @@ -156,9 +157,18 @@ static Indirect *ext4_get_branch(struct inode *inode, int depth, if (!p->key) goto no_block; while (--depth) { - bh = sb_getblk(sb, le32_to_cpu(p->key)); + key = le32_to_cpu(p->key); + bh = sb_getblk(sb, key); if (unlikely(!bh)) { - ret = -ENOMEM; + /* + * sb_getblk() masks different errors by always + * returning NULL. Let's distinguish at least the case + * where the block is out of range. + */ + if (key > ext4_blocks_count(EXT4_SB(sb)->s_es)) + ret = -EFSCORRUPTED; + else + ret = -ENOMEM; goto failure; }
