Use the ATTR_FILE attribute to distinguish between truncate()
and ftruncate() system calls. The two other cases where
do_truncate is called with a filp (and therefore ATTR_FILE is set)
are for coredump files and for open(O_TRUNC). In both of those cases
the open permission has already been checked during file open and
therefore does not need to be repeated.
Commit 95dbf739313f ("SELinux: check OPEN on truncate calls")
fixed a major issue where domains were allowed to truncate files
without the open permission. However, it introduced a new bug where
a domain with the write permission can no longer ftruncate files
without the open permission, even when they receive an already open
file.
Signed-off-by: Jeff Vander Stoep <jeffv@xxxxxxxxxx>
---
V2 fixes mistakes in commit message
security/selinux/hooks.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
index f4be0a1..b32f1e1 100644
--- a/security/selinux/hooks.c
+++ b/security/selinux/hooks.c
@@ -2934,7 +2934,8 @@ 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))
+ if (selinux_policycap_openperm && (ia_valid & ATTR_SIZE)
+ && !(ia_valid & ATTR_FILE))
av |= FILE__OPEN;
return dentry_has_perm(cred, dentry, av);
--
2.6.0.rc0.131.gf624c3d
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