5.4-stable review patch. If anyone has any objections, please let me know.
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From: Jann Horn jannh@google.com
[ Upstream commit 642335f3ea2b3fd6dba03e57e01fa9587843a497 ]
A file handle that userspace provides to open_by_handle_at() can legitimately contain an outdated inode number that has since been reused for another purpose - that's why the file handle also contains a generation number.
But if the inode number has been reused for an ea_inode, check_igot_inode() will notice, __ext4_iget() will go through ext4_error_inode(), and if the inode was newly created, it will also be marked as bad by iget_failed(). This all happens before the point where the inode generation is checked.
ext4_error_inode() is supposed to only be used on filesystem corruption; it should not be used when userspace just got unlucky with a stale file handle. So when this happens, let __ext4_iget() just return an error.
Fixes: b3e6bcb94590 ("ext4: add EA_INODE checking to ext4_iget()") Signed-off-by: Jann Horn jannh@google.com Reviewed-by: Jan Kara jack@suse.cz Link: https://patch.msgid.link/20241129-ext4-ignore-ea-fhandle-v1-1-e532c0d1cee0@g... Signed-off-by: Theodore Ts'o tytso@mit.edu Signed-off-by: Sasha Levin sashal@kernel.org --- fs/ext4/inode.c | 68 ++++++++++++++++++++++++++++++++++--------------- 1 file changed, 48 insertions(+), 20 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 0289a9e36d355..8f020c719b18d 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -4893,22 +4893,43 @@ static inline u64 ext4_inode_peek_iversion(const struct inode *inode) return inode_peek_iversion(inode); }
-static const char *check_igot_inode(struct inode *inode, ext4_iget_flags flags) - +static int check_igot_inode(struct inode *inode, ext4_iget_flags flags, + const char *function, unsigned int line) { + const char *err_str; + if (flags & EXT4_IGET_EA_INODE) { - if (!(EXT4_I(inode)->i_flags & EXT4_EA_INODE_FL)) - return "missing EA_INODE flag"; + if (!(EXT4_I(inode)->i_flags & EXT4_EA_INODE_FL)) { + err_str = "missing EA_INODE flag"; + goto error; + } if (ext4_test_inode_state(inode, EXT4_STATE_XATTR) || - EXT4_I(inode)->i_file_acl) - return "ea_inode with extended attributes"; + EXT4_I(inode)->i_file_acl) { + err_str = "ea_inode with extended attributes"; + goto error; + } } else { - if ((EXT4_I(inode)->i_flags & EXT4_EA_INODE_FL)) - return "unexpected EA_INODE flag"; + if ((EXT4_I(inode)->i_flags & EXT4_EA_INODE_FL)) { + /* + * open_by_handle_at() could provide an old inode number + * that has since been reused for an ea_inode; this does + * not indicate filesystem corruption + */ + if (flags & EXT4_IGET_HANDLE) + return -ESTALE; + err_str = "unexpected EA_INODE flag"; + goto error; + } + } + if (is_bad_inode(inode) && !(flags & EXT4_IGET_BAD)) { + err_str = "unexpected bad inode w/o EXT4_IGET_BAD"; + goto error; } - if (is_bad_inode(inode) && !(flags & EXT4_IGET_BAD)) - return "unexpected bad inode w/o EXT4_IGET_BAD"; - return NULL; + return 0; + +error: + ext4_error_inode(inode, function, line, 0, err_str); + return -EFSCORRUPTED; }
struct inode *__ext4_iget(struct super_block *sb, unsigned long ino, @@ -4919,7 +4940,6 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino, struct ext4_inode *raw_inode; struct ext4_inode_info *ei; struct inode *inode; - const char *err_str; journal_t *journal = EXT4_SB(sb)->s_journal; long ret; loff_t size; @@ -4944,10 +4964,10 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino, if (!inode) return ERR_PTR(-ENOMEM); if (!(inode->i_state & I_NEW)) { - if ((err_str = check_igot_inode(inode, flags)) != NULL) { - ext4_error_inode(inode, function, line, 0, err_str); + ret = check_igot_inode(inode, flags, function, line); + if (ret) { iput(inode); - return ERR_PTR(-EFSCORRUPTED); + return ERR_PTR(ret); } return inode; } @@ -5218,13 +5238,21 @@ struct inode *__ext4_iget(struct super_block *sb, unsigned long ino, ret = -EFSCORRUPTED; goto bad_inode; } - if ((err_str = check_igot_inode(inode, flags)) != NULL) { - ext4_error_inode(inode, function, line, 0, err_str); - ret = -EFSCORRUPTED; - goto bad_inode; + ret = check_igot_inode(inode, flags, function, line); + /* + * -ESTALE here means there is nothing inherently wrong with the inode, + * it's just not an inode we can return for an fhandle lookup. + */ + if (ret == -ESTALE) { + brelse(iloc.bh); + unlock_new_inode(inode); + iput(inode); + return ERR_PTR(-ESTALE); } - + if (ret) + goto bad_inode; brelse(iloc.bh); + unlock_new_inode(inode); return inode;