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selinux: do not check open permission on sockets 

open permission is currently only defined for files in the kernel
(COMMON_FILE_PERMS rather than COMMON_FILE_SOCK_PERMS). Construction of
an artificial test case that tries to open a socket via /proc/pid/fd will
generate a recvfrom avc denial because recvfrom and open happen to map to
the same permission bit in socket vs file classes.

open of a socket via /proc/pid/fd is not supported by the kernel regardless
and will ultimately return ENXIO. But we hit the permission check first and
can thus produce these odd/misleading denials.  Omit the open check when
operating on a socket.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Paul Moore <paul@paul-moore.com>
zero-colors
Stephen Smalley 2017-05-12 12:41:24 -04:00 committed by Paul Moore
parent 3ba4bf5f1e
commit ccb544781d
1 changed files with 7 additions and 3 deletions
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10
security/selinux/hooks.c
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@ -2063,8 +2063,9 @@ static inline u32 file_to_av(struct file *file)
static inline u32 open_file_to_av(struct file *file)
{
u32 av = file_to_av(file);
struct inode *inode = file_inode(file);
if (selinux_policycap_openperm)
if (selinux_policycap_openperm && inode->i_sb->s_magic != SOCKFS_MAGIC)
av |= FILE__OPEN;
return av;
@ -3059,6 +3060,7 @@ static int selinux_inode_permission(struct inode *inode, int mask)
static int selinux_inode_setattr(struct dentry *dentry, struct iattr *iattr)
{
const struct cred *cred = current_cred();
struct inode *inode = d_backing_inode(dentry);
unsigned int ia_valid = iattr->ia_valid;
__u32 av = FILE__WRITE;
@ -3074,8 +3076,10 @@ static int selinux_inode_setattr(struct dentry *dentry, struct iattr *iattr)
ATTR_ATIME_SET | ATTR_MTIME_SET | ATTR_TIMES_SET))
return dentry_has_perm(cred, dentry, FILE__SETATTR);
if (selinux_policycap_openperm && (ia_valid & ATTR_SIZE)
&& !(ia_valid & ATTR_FILE))
if (selinux_policycap_openperm &&
inode->i_sb->s_magic != SOCKFS_MAGIC &&
(ia_valid & ATTR_SIZE) &&
!(ia_valid & ATTR_FILE))
av |= FILE__OPEN;
return dentry_has_perm(cred, dentry, av);