Re: [PATCH 1/2] prctl: take mmap sem for writing to protect against others

[Anshuman Khandual]

On Wed, Jan 6, 2016 at 10:32 AM, Mateusz Guzik <mguzik@xxxxxxxxxx> wrote:
> The code was taking the semaphore for reading, which does not protect
> against readers nor concurrent modifications.

(down/up)_read does not protect against concurrent readers ?

>
> The problem could cause a sanity checks to fail in procfs's cmdline
> reader, resulting in an OOPS.
>

Can you explain this a bit and may be give some examples ?

> Note that some functions perform an unlocked read of various mm fields,
> but they seem to be fine despite possible modificaton.

Those need to be fixed as well ?

> Signed-off-by: Mateusz Guzik <mguzik@xxxxxxxxxx>
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