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ext4: add EXT4_IGET_BAD flag to prevent unexpected bad inode 

There are many places that will get unhappy (and crash) when ext4_iget()
returns a bad inode. However, if iget the boot loader inode, allows a bad
inode to be returned, because the inode may not be initialized. This
mechanism can be used to bypass some checks and cause panic. To solve this
problem, we add a special iget flag EXT4_IGET_BAD. Only with this flag
we'd be returning bad inode from ext4_iget(), otherwise we always return
the error code if the inode is bad inode.(suggested by Jan Kara)

Signed-off-by: Baokun Li <libaokun1@huawei.com>
Reviewed-by: Jason Yan <yanaijie@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20221026042310.3839669-4-libaokun1@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org
This commit is contained in:
Baokun Li 2022-10-26 12:23:09 +08:00 committed by Theodore Ts'o
parent 07342ec259
commit 63b1e9bccb
3 changed files with 11 additions and 3 deletions
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3
fs/ext4/ext4.h
View File

@ -2964,7 +2964,8 @@ int do_journal_get_write_access(handle_t *handle, struct inode *inode,
typedef enum {
EXT4_IGET_NORMAL = 0,
EXT4_IGET_SPECIAL = 0x0001, /* OK to iget a system inode */
EXT4_IGET_HANDLE = 0x0002 /* Inode # is from a handle */
EXT4_IGET_HANDLE = 0x0002, /* Inode # is from a handle */
EXT4_IGET_BAD = 0x0004 /* Allow to iget a bad inode */
} ext4_iget_flags;
extern struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,

8
fs/ext4/inode.c
View File

@ -5058,8 +5058,14 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino,
if (IS_CASEFOLDED(inode) && !ext4_has_feature_casefold(inode->i_sb))
ext4_error_inode(inode, function, line, 0,
"casefold flag without casefold feature");
brelse(iloc.bh);
if (is_bad_inode(inode) && !(flags & EXT4_IGET_BAD)) {
ext4_error_inode(inode, function, line, 0,
"bad inode without EXT4_IGET_BAD flag");
ret = -EUCLEAN;
goto bad_inode;
}
brelse(iloc.bh);
unlock_new_inode(inode);
return inode;

3
fs/ext4/ioctl.c
View File

@ -374,7 +374,8 @@ static long swap_inode_boot_loader(struct super_block *sb,
blkcnt_t blocks;
unsigned short bytes;
inode_bl = ext4_iget(sb, EXT4_BOOT_LOADER_INO, EXT4_IGET_SPECIAL);
inode_bl = ext4_iget(sb, EXT4_BOOT_LOADER_INO,
EXT4_IGET_SPECIAL | EXT4_IGET_BAD);
if (IS_ERR(inode_bl))
return PTR_ERR(inode_bl);
ei_bl = EXT4_I(inode_bl);