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cap: fix conversions on getxattr

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If a capability is stored on disk in v2 format cap_inode_getsecurity() will
currently return in v2 format unconditionally.

This is wrong: v2 cap should be equivalent to a v3 cap with zero rootid,
and so the same conversions performed on it.

If the rootid cannot be mapped, v3 is returned unconverted.  Fix this so
that both v2 and v3 return -EOVERFLOW if the rootid (or the owner of the fs
user namespace in case of v2) cannot be mapped into the current user
namespace.

Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
This commit is contained in:
Miklos Szeredi 2021-01-28 10:22:48 +01:00
parent 554677b972
commit f2b00be488
1 changed files with 43 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

67
security/commoncap.c
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@ -371,10 +371,11 @@ int cap_inode_getsecurity(struct inode *inode, const char *name, void **buffer,
{
int size, ret;
kuid_t kroot;
u32 nsmagic, magic;
uid_t root, mappedroot;
char *tmpbuf = NULL;
struct vfs_cap_data *cap;
struct vfs_ns_cap_data *nscap;
struct vfs_ns_cap_data *nscap = NULL;
struct dentry *dentry;
struct user_namespace *fs_ns;
@ -396,46 +397,61 @@ int cap_inode_getsecurity(struct inode *inode, const char *name, void **buffer,
fs_ns = inode->i_sb->s_user_ns;
cap = (struct vfs_cap_data *) tmpbuf;
if (is_v2header((size_t) ret, cap)) {
/* If this is sizeof(vfs_cap_data) then we're ok with the
* on-disk value, so return that. */
if (alloc)
*buffer = tmpbuf;
else
kfree(tmpbuf);
return ret;
} else if (!is_v3header((size_t) ret, cap)) {
kfree(tmpbuf);
return -EINVAL;
root = 0;
} else if (is_v3header((size_t) ret, cap)) {
nscap = (struct vfs_ns_cap_data *) tmpbuf;
root = le32_to_cpu(nscap->rootid);
} else {
size = -EINVAL;
goto out_free;
}
nscap = (struct vfs_ns_cap_data *) tmpbuf;
root = le32_to_cpu(nscap->rootid);
kroot = make_kuid(fs_ns, root);
/* If the root kuid maps to a valid uid in current ns, then return
* this as a nscap. */
mappedroot = from_kuid(current_user_ns(), kroot);
if (mappedroot != (uid_t)-1 && mappedroot != (uid_t)0) {
size = sizeof(struct vfs_ns_cap_data);
if (alloc) {
*buffer = tmpbuf;
if (!nscap) {
/* v2 -> v3 conversion */
nscap = kzalloc(size, GFP_ATOMIC);
if (!nscap) {
size = -ENOMEM;
goto out_free;
}
nsmagic = VFS_CAP_REVISION_3;
magic = le32_to_cpu(cap->magic_etc);
if (magic & VFS_CAP_FLAGS_EFFECTIVE)
nsmagic |= VFS_CAP_FLAGS_EFFECTIVE;
memcpy(&nscap->data, &cap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
nscap->magic_etc = cpu_to_le32(nsmagic);
} else {
/* use allocated v3 buffer */
tmpbuf = NULL;
}
nscap->rootid = cpu_to_le32(mappedroot);
} else
kfree(tmpbuf);
return size;
*buffer = nscap;
}
goto out_free;
}
if (!rootid_owns_currentns(kroot)) {
kfree(tmpbuf);
return -EOPNOTSUPP;
size = -EOVERFLOW;
goto out_free;
}
/* This comes from a parent namespace. Return as a v2 capability */
size = sizeof(struct vfs_cap_data);
if (alloc) {
*buffer = kmalloc(size, GFP_ATOMIC);
if (*buffer) {
struct vfs_cap_data *cap = *buffer;
__le32 nsmagic, magic;
if (nscap) {
/* v3 -> v2 conversion */
cap = kzalloc(size, GFP_ATOMIC);
if (!cap) {
size = -ENOMEM;
goto out_free;
}
magic = VFS_CAP_REVISION_2;
nsmagic = le32_to_cpu(nscap->magic_etc);
if (nsmagic & VFS_CAP_FLAGS_EFFECTIVE)
@ -443,9 +459,12 @@ int cap_inode_getsecurity(struct inode *inode, const char *name, void **buffer,
memcpy(&cap->data, &nscap->data, sizeof(__le32) * 2 * VFS_CAP_U32);
cap->magic_etc = cpu_to_le32(magic);
} else {
size = -ENOMEM;
/* use unconverted v2 */
tmpbuf = NULL;
}
*buffer = cap;
}
out_free:
kfree(tmpbuf);
return size;
}