2007-02-01 14:57:45

by Alexey Dobriyan

Subject: [RFC] Allow access to /proc/$PID/fd after setuid()

/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)

Signed-off-by: Alexey Dobriyan <[email protected]>
---

fs/proc/base.c | 16 ++++++++++++++++
1 file changed, 16 insertions(+)

--- a/fs/proc/base.c
+++ b/fs/proc/base.c
@@ -1413,11 +1413,27 @@ static struct file_operations proc_fd_op
.readdir = proc_readfd,
};

+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 == 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,
};

2007-02-01 15:05:23

by Kirill Korotaev

Subject: Re: [Devel] [RFC] Allow access to /proc/$PID/fd after setuid()

Acked-By: Kirill Korotaev <[email protected]>

> /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)
>
> Signed-off-by: Alexey Dobriyan <[email protected]>
> ---
>
> fs/proc/base.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -1413,11 +1413,27 @@ static struct file_operations proc_fd_op
> .readdir = proc_readfd,
> };
>
> +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 == 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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