4.9-stable review patch. If anyone has any objections, please let me know.
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From: Gustavo A. R. Silva gustavo@embeddedor.com
commit fee05f455ceb5c670cbe48e2f9454ebc4a388554 upstream.
req.gid 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:
vers/misc/sgi-gru/grukdump.c:200 gru_dump_chiplet_request() warn: potential spectre issue 'gru_base' [w]
Fix this by sanitizing req.gid before calling macro GID_TO_GRU, which uses it to index gru_base.
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: Gustavo A. R. Silva gustavo@embeddedor.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/misc/sgi-gru/grukdump.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/drivers/misc/sgi-gru/grukdump.c +++ b/drivers/misc/sgi-gru/grukdump.c @@ -27,6 +27,9 @@ #include <linux/delay.h> #include <linux/bitops.h> #include <asm/uv/uv_hub.h> + +#include <linux/nospec.h> + #include "gru.h" #include "grutables.h" #include "gruhandles.h" @@ -196,6 +199,7 @@ int gru_dump_chiplet_request(unsigned lo /* Currently, only dump by gid is implemented */ if (req.gid >= gru_max_gids) return -EINVAL; + req.gid = array_index_nospec(req.gid, gru_max_gids);
gru = GID_TO_GRU(req.gid); ubuf = req.buf;