On Wed, Feb 22, 2012 at 2:23 AM, Ingo Molnar <mingo@xxxxxxx> wrote:
>
> * Kees Cook <keescook@xxxxxxxxxxxx> wrote:
>
>> Clean-up of hardlink restriction logic, as suggested by Andrew Morton.
>>
>> Signed-off-by: Kees Cook <keescook@xxxxxxxxxxxx>
>> ---
>> fs/namei.c | 59 +++++++++++++++++++++++++++++++++++++++++------------------
>> 1 files changed, 41 insertions(+), 18 deletions(-)
>>
>> diff --git a/fs/namei.c b/fs/namei.c
>> index 8ed4e00..a4a21a5 100644
>> --- a/fs/namei.c
>> +++ b/fs/namei.c
>> @@ -693,46 +693,69 @@ static inline int may_follow_link(struct path *link)
>> }
>>
>> /**
>> + * safe_hardlink_source - Check for safe hardlink conditions
>> + * @inode: the source inode to hardlink from
>> + *
>> + * Return false if at least one of the following conditions:
>> + * - inode is not a regular file
>> + * - inode is setuid
>> + * - inode is setgid and group-exec
>> + * - access failure for read and write
>> + *
>> + * Otherwise returns true.
>> + */
>> +static bool safe_hardlink_source(struct inode *inode)
>> +{
>> + mode_t mode = inode->i_mode;
>> +
>> + /* Special files should not get pinned to the filesystem. */
>> + if (!S_ISREG(mode))
>> + return false;
>> + /* Setuid files should not get pinned to the filesystem. */
>> + if (mode & S_ISUID)
>> + return false;
>> + /* Executable setgid files should not get pinned to the filesystem. */
>> + if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
>> + return false;
>> + /* Hardlinking to unreadable or unwritable sources is dangerous. */
>> + if (inode_permission(inode, MAY_READ | MAY_WRITE))
>> + return false;
>> +
>> + return true;
>
> A really minor nitpick, could we use this form please:
>
> static bool safe_hardlink_source(struct inode *inode)
> {
> mode_t mode = inode->i_mode;
>
> /* Special files should not get pinned to the filesystem. */
> if (!S_ISREG(mode))
> return false;
>
> /* Setuid files should not get pinned to the filesystem. */
> if (mode & S_ISUID)
> return false;
>
> /* Executable setgid files should not get pinned to the filesystem. */
> if ((mode & (S_ISGID | S_IXGRP)) == (S_ISGID | S_IXGRP))
> return false;
>
> /* Hardlinking to unreadable or unwritable sources is dangerous. */
> if (inode_permission(inode, MAY_READ | MAY_WRITE))
> return false;
>
> return true;
> }
>
> Those separate blocks of comments and conditions stand out much
> nicer this way, making it way easier on the eyes - to my eyes at
> least ;-)
Heh, sure. I've sent v2 now. :)
-Kees
--
Kees Cook
ChromeOS Security
--
To unsubscribe from this list: send the line "unsubscribe linux-doc" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
