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userns: Allow any uid or gid mappings that don't overlap.

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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>
This commit is contained in:
Eric W. Biederman 2012-12-27 22:27:29 -08:00
parent c61a2810a2
commit 0bd14b4fd7
1 changed files with 39 additions and 6 deletions
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45
kernel/user_namespace.c
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@ -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) &&