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Date: Fri, 17 Feb 2017 13:24:15 -0500 From: Stephen Smalley <sds@...ho.nsa.gov> To: viro@...iv.linux.org.uk Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, linux-security-module@...r.kernel.org, selinux@...ho.nsa.gov, Stephen Smalley <sds@...ho.nsa.gov> Subject: [PATCH] fs: switch order of CAP_DAC_OVERRIDE and CAP_DAC_READ_SEARCH checks 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@...ho.nsa.gov> --- fs/namei.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index ad74877..8736e4a 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -340,22 +340,14 @@ int generic_permission(struct inode *inode, int mask) if (S_ISDIR(inode->i_mode)) { /* DACs are overridable for directories */ - if (capable_wrt_inode_uidgid(inode, CAP_DAC_OVERRIDE)) - return 0; if (!(mask & MAY_WRITE)) if (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH)) 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)) return 0; + return -EACCES; + } /* * 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 (capable_wrt_inode_uidgid(inode, CAP_DAC_READ_SEARCH)) 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; } -- 2.7.4
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