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Commit ad43aede authored by Gustavo A. R. Silva's avatar Gustavo A. R. Silva Committed by Greg Kroah-Hartman
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atm: zatm: Fix potential Spectre v1 

commit 2be147f7459db5bbf292e0a6f135037b55e20b39 upstream.

pool can be indirectly controlled by user-space, hence leading to
a potential exploitation of the Spectre variant 1 vulnerability.

This issue was detected with the help of Smatch:

drivers/atm/zatm.c:1462 zatm_ioctl() warn: potential spectre issue
'zatm_dev->pool_info' (local cap)

Fix this by sanitizing pool before using it to index
zatm_dev->pool_info

Notice that given that speculation windows are large, the policy is
to kill the speculation on the first load and not worry if it can be
completed with a dependent load/store [1].

[1] https://marc.info/?l=linux-kernel&m=152449131114778&w=2



Cc: stable@vger.kernel.org
Signed-off-by: default avatarGustavo A. R. Silva <gustavo@embeddedor.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 81b8eb6b

drivers/atm/zatm.c

+3 −0
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 
#include <linux/bitops.h>

#include <linux/wait.h>

#include <linux/slab.h>

#include <linux/nospec.h>

#include <asm/byteorder.h>

#include <asm/string.h>

#include <asm/io.h>
@@ -1458,6 +1459,8 @@ static int zatm_ioctl(struct atm_dev *dev,unsigned int cmd,void __user *arg) 
					return -EFAULT;

				if (pool < 0 || pool > ZATM_LAST_POOL)

					return -EINVAL;

				pool = array_index_nospec(pool,

							  ZATM_LAST_POOL + 1);

				spin_lock_irqsave(&zatm_dev->lock, flags);

				info = zatm_dev->pool_info[pool];

				if (cmd == ZATM_GETPOOLZ) {