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fs: switch order of CAP_DAC_OVERRIDE and CAP_DAC_READ_SEARCH checks

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generic_permission() presently checks CAP_DAC_OVERRIDE prior to
CAP_DAC_READ_SEARCH.  This can cause misleading audit messages when
using a LSM such as SELinux or AppArmor, since CAP_DAC_OVERRIDE
may not be required for the operation.  Flip the order of the
tests so that CAP_DAC_OVERRIDE is only checked when required for
the operation.

Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
Acked-by: John Johansen <john.johansen@canonical.com>
Reviewed-by: Serge Hallyn <serge@hallyn.com>
Acked-by: James Morris <james.l.morris@oracle.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
This commit is contained in:
Stephen Smalley 2017-03-10 12:14:18 -05:00 committed by Paul Moore
parent 710a0647ba
commit 2a4c224269
1 changed files with 10 additions and 10 deletions
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20
fs/namei.c
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@ -340,22 +340,14 @@ int generic_permission(struct inode *inode, int mask)
if (S_ISDIR(inode->i_mode)) { if (S_ISDIR(inode->i_mode)) {
/* DACs are overridable for directories */ /* DACs are overridable for directories */
if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
return 0;
if (!(mask & MAY_WRITE)) if (!(mask & MAY_WRITE))
if (capable_wrt_inode_uidgid(inode, if (capable_wrt_inode_uidgid(inode,
CAP_DAC_READ_SEARCH)) CAP_DAC_READ_SEARCH))
return 0; return 0;
return -EACCES;
}
/*
* Read/write DACs are always overridable.
* Executable DACs are overridable when there is
* at least one exec bit set.
*/
if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
return 0; return 0;
return -EACCES;
}
/* /*
* Searching includes executable on directories, else just read. * Searching includes executable on directories, else just read.
@ -364,6 +356,14 @@ int generic_permission(struct inode *inode, int mask)
if (mask == MAY_READ) if (mask == MAY_READ)
if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH)) if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH))
return 0; return 0;
/*
* Read/write DACs are always overridable.
* Executable DACs are overridable when there is
* at least one exec bit set.
*/
if (!(mask & MAY_EXEC) || (inode->i_mode & S_IXUGO))
if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE))
return 0;
return -EACCES; return -EACCES;
} }