crap, Pavel reminded that get_proc_task() can return NULL.
------------------------------------------------------------------------
/proc/$PID/fd has r-x------ permissions, so if process does setuid(), it
will not be able to access /proc/*/fd/. This breaks fstatat() emulation
in glibc.
open("foo", O_RDONLY|O_DIRECTORY) = 4
setuid32(65534) = 0
stat64("/proc/self/fd/4/bar", 0xbfafb298) = -1 EACCES (Permission denied)
Comment from Andrew Morton.
Signed-off-by: Alexey Dobriyan <[email protected]>
---
fs/proc/base.c | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1414,10 +1414,33 @@ static struct file_operations proc_fd_op
};
/*
+ * /proc/pid/fd needs a special permission handler so that a process can still
+ * access /proc/self/fd after it has executed a setuid().
+ */
+static int proc_fd_permission(struct inode *inode, int mask,
+ struct nameidata *nd)
+{
+ struct task_struct *tsk;
+ int rv;
+
+ rv = generic_permission(inode, mask, NULL);
+ if (rv == 0)
+ return 0;
+ tsk = get_proc_task(inode);
+ if (tsk) {
+ if (tsk == current)
+ rv = 0;
+ put_task_struct(tsk);
+ }
+ return rv;
+}
+
+/*
* proc directories can do almost nothing..
*/
static struct inode_operations proc_fd_inode_operations = {
.lookup = proc_lookupfd,
+ .permission = proc_fd_permission,
.setattr = proc_setattr,
};
-
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