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pagemap: do not leak physical addresses to non-privileged userspace
As pointed by recent post[1] on exploiting DRAM physical imperfection, /proc/PID/pagemap exposes sensitive information which can be used to do attacks. This disallows anybody without CAP_SYS_ADMIN to read the pagemap. [1] http://googleprojectzero.blogspot.com/2015/03/exploiting-dram-rowhammer-bug-to-gain.html [ Eventually we might want to do anything more finegrained, but for now this is the simple model. - Linus ] Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Acked-by: Konstantin Khlebnikov <khlebnikov@openvz.org> Acked-by: Andy Lutomirski <luto@amacapital.net> Cc: Pavel Emelyanov <xemul@parallels.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Mark Seaborn <mseaborn@chromium.org> Cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -1325,6 +1325,9 @@ out:
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static int pagemap_open(struct inode *inode, struct file *file)
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{
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/* do not disclose physical addresses: attack vector */
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if (!capable(CAP_SYS_ADMIN))
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return -EPERM;
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pr_warn_once("Bits 55-60 of /proc/PID/pagemap entries are about "
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"to stop being page-shift some time soon. See the "
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"linux/Documentation/vm/pagemap.txt for details.\n");
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