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SubjectRe: [PATCH] Set bounds on what /proc/self/make-it-fail accepts.
On Tue, 18 Feb 2014 17:06:06 -0500 Dave Jones <davej@redhat.com> wrote:

> /proc/self/make-it-fail is a boolean, but accepts any number, including
> negative ones. Change variable to unsigned, and cap upper bound at 1.
>
> Signed-off-by: Dave Jones <davej@fedoraproject.org>
>
> diff --git a/fs/proc/base.c b/fs/proc/base.c
> index 51507065263b..b926377c354f 100644
> --- a/fs/proc/base.c
> +++ b/fs/proc/base.c
> @@ -1207,7 +1207,7 @@ static ssize_t proc_fault_inject_read(struct file * file, char __user * buf,
> struct task_struct *task = get_proc_task(file_inode(file));
> char buffer[PROC_NUMBUF];
> size_t len;
> - int make_it_fail;
> + unsigned int make_it_fail;
>
> if (!task)
> return -ESRCH;
> @@ -1224,7 +1224,7 @@ static ssize_t proc_fault_inject_write(struct file * file,
> {
> struct task_struct *task;
> char buffer[PROC_NUMBUF], *end;
> - int make_it_fail;
> + unsigned int make_it_fail;
>
> if (!capable(CAP_SYS_RESOURCE))
> return -EPERM;
> @@ -1236,6 +1236,9 @@ static ssize_t proc_fault_inject_write(struct file * file,
> make_it_fail = simple_strtol(strstrip(buffer), &end, 0);
> if (*end)
> return -EINVAL;
> + if (make_it_fail > 1)
> + return -EINVAL;
> +
> task = get_proc_task(file_inode(file));
> if (!task)
> return -ESRCH;

Switching `make_it_fail' to unsigned makes the test simpler but it does
rather muck up the typing in there. task_struct.make_it_fail is still
an int, we should now use simple_strtoul rather than simple_strtol,
proc_fault_inject_read()'s snprintf() should now use %u, etc. None of
which actually matters, but still...

Rather than address all that I'm inclined to leave `make_it_fail' as an
int, turning your patch into a one-liner?

--- a/fs/proc/base.c~fault-injection-set-bounds-on-what-proc-self-make-it-fail-accepts-fix
+++ a/fs/proc/base.c
@@ -1207,7 +1207,7 @@ static ssize_t proc_fault_inject_read(st
struct task_struct *task = get_proc_task(file_inode(file));
char buffer[PROC_NUMBUF];
size_t len;
- unsigned int make_it_fail;
+ int make_it_fail;

if (!task)
return -ESRCH;
@@ -1224,7 +1224,7 @@ static ssize_t proc_fault_inject_write(s
{
struct task_struct *task;
char buffer[PROC_NUMBUF], *end;
- unsigned int make_it_fail;
+ int make_it_fail;

if (!capable(CAP_SYS_RESOURCE))
return -EPERM;
@@ -1236,7 +1236,7 @@ static ssize_t proc_fault_inject_write(s
make_it_fail = simple_strtol(strstrip(buffer), &end, 0);
if (*end)
return -EINVAL;
- if (make_it_fail > 1)
+ if (make_it_fail < 0 || make_it_fail > 1)
return -EINVAL;

task = get_proc_task(file_inode(file));
_


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