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Date: Tue, 8 Aug 2017 14:44:41 +0200 From: Jan Kara <jack@...e.cz> To: stable@...r.kernel.org Cc: Ted Tso <tytso@....edu>, <linux-ext4@...r.kernel.org>, gregkh@...uxfoundation.org, Ernesto A. Fernández <ernesto.mnd.fernandez@...il.com> Subject: [PATCH 1/2] ext4: preserve i_mode if __ext4_set_acl() fails From: Ernesto A. Fernández <ernesto.mnd.fernandez@...il.com> When changing a file's acl mask, __ext4_set_acl() will first set the group bits of i_mode to the value of the mask, and only then set the actual extended attribute representing the new acl. If the second part fails (due to lack of space, for example) and the file had no acl attribute to begin with, the system will from now on assume that the mask permission bits are actual group permission bits, potentially granting access to the wrong users. Prevent this by only changing the inode mode after the acl has been set. Signed-off-by: Ernesto A. Fernández <ernesto.mnd.fernandez@...il.com> Signed-off-by: Theodore Ts'o <tytso@....edu> Reviewed-by: Jan Kara <jack@...e.cz> --- fs/ext4/acl.c | 15 +++++++++++---- 1 file changed, 11 insertions(+), 4 deletions(-) --- a/fs/ext4/acl.c +++ b/fs/ext4/acl.c @@ -189,16 +189,17 @@ __ext4_set_acl(handle_t *handle, struct void *value = NULL; size_t size = 0; int error; + int update_mode = 0; + umode_t mode = inode->i_mode; switch (type) { case ACL_TYPE_ACCESS: name_index = EXT4_XATTR_INDEX_POSIX_ACL_ACCESS; if (acl) { - error = posix_acl_update_mode(inode, &inode->i_mode, &acl); + error = posix_acl_update_mode(inode, &mode, &acl); if (error) return error; - inode->i_ctime = current_time(inode); - ext4_mark_inode_dirty(handle, inode); + update_mode = 1; } break; @@ -221,8 +222,14 @@ __ext4_set_acl(handle_t *handle, struct value, size, 0); kfree(value); - if (!error) + if (!error) { set_cached_acl(inode, type, acl); + if (update_mode) { + inode->i_mode = mode; + inode->i_ctime = current_time(inode); + ext4_mark_inode_dirty(handle, inode); + } + } return error; }
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