diff options
| author | Eric W. Biederman <ebiederm@xmission.com> | 2012-12-27 22:27:29 -0800 |
|---|---|---|
| committer | Eric W. Biederman <ebiederm@xmission.com> | 2013-01-26 22:12:04 -0800 |
| commit | 0bd14b4fd72afd5df41e9fd59f356740f22fceba (patch) | |
| tree | bf1bc8dfa507ca40970927efb2dd87b4f5bdd416 /kernel/user_namespace.c | |
| parent | c61a2810a2161986353705b44d9503e6bb079f4f (diff) | |
userns: Allow any uid or gid mappings that don't overlap.
When I initially wrote the code for /proc/<pid>/uid_map. I was lazy
and avoided duplicate mappings by the simple expedient of ensuring the
first number in a new extent was greater than any number in the
previous extent.
Unfortunately that precludes a number of valid mappings, and someone
noticed and complained. So use a simple check to ensure that ranges
in the mapping extents don't overlap.
Acked-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
Diffstat (limited to 'kernel/user_namespace.c')
| -rw-r--r-- | kernel/user_namespace.c | 45 |
1 files changed, 39 insertions, 6 deletions
diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 24f8ec3b64d8..8b650837083e 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -520,6 +520,42 @@ struct seq_operations proc_projid_seq_operations = { .show = projid_m_show, }; +static bool mappings_overlap(struct uid_gid_map *new_map, struct uid_gid_extent *extent) +{ + u32 upper_first, lower_first, upper_last, lower_last; + unsigned idx; + + upper_first = extent->first; + lower_first = extent->lower_first; + upper_last = upper_first + extent->count - 1; + lower_last = lower_first + extent->count - 1; + + for (idx = 0; idx < new_map->nr_extents; idx++) { + u32 prev_upper_first, prev_lower_first; + u32 prev_upper_last, prev_lower_last; + struct uid_gid_extent *prev; + + prev = &new_map->extent[idx]; + + prev_upper_first = prev->first; + prev_lower_first = prev->lower_first; + prev_upper_last = prev_upper_first + prev->count - 1; + prev_lower_last = prev_lower_first + prev->count - 1; + + /* Does the upper range intersect a previous extent? */ + if ((prev_upper_first <= upper_last) && + (prev_upper_last >= upper_first)) + return true; + + /* Does the lower range intersect a previous extent? */ + if ((prev_lower_first <= lower_last) && + (prev_lower_last >= lower_first)) + return true; + } + return false; +} + + static DEFINE_MUTEX(id_map_mutex); static ssize_t map_write(struct file *file, const char __user *buf, @@ -532,7 +568,7 @@ static ssize_t map_write(struct file *file, const char __user *buf, struct user_namespace *ns = seq->private; struct uid_gid_map new_map; unsigned idx; - struct uid_gid_extent *extent, *last = NULL; + struct uid_gid_extent *extent = NULL; unsigned long page = 0; char *kbuf, *pos, *next_line; ssize_t ret = -EINVAL; @@ -635,14 +671,11 @@ static ssize_t map_write(struct file *file, const char __user *buf, if ((extent->lower_first + extent->count) <= extent->lower_first) goto out; - /* For now only accept extents that are strictly in order */ - if (last && - (((last->first + last->count) > extent->first) || - ((last->lower_first + last->count) > extent->lower_first))) + /* Do the ranges in extent overlap any previous extents? */ + if (mappings_overlap(&new_map, extent)) goto out; new_map.nr_extents++; - last = extent; /* Fail if the file contains too many extents */ if ((new_map.nr_extents == UID_GID_MAP_MAX_EXTENTS) && |