[PATCH 5.4 029/108] misc: fastrpc: fix memory corruption on open

Greg Kroah-Hartman
2022-09-13T15:05:33Z

From: Johan Hovold <johan+linaro@kernel.org>

commit d245f43aab2b61195d8ebb64cef7b5a08c590ab4 upstream.

The probe session-duplication overflow check incremented the session
count also when there were no more available sessions so that memory
beyond the fixed-size slab-allocated session array could be corrupted in
fastrpc_session_alloc() on open().

Fixes: f6f9279f2bf0 ("misc: fastrpc: Add Qualcomm fastrpc basic driver model")
Cc: stable@vger.kernel.org # 5.1
Signed-off-by: Johan Hovold <johan+linaro@kernel.org>
Link: https://lore.kernel.org/r/20220829080531.29681-3-johan+linaro@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/misc/fastrpc.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)

--- a/drivers/misc/fastrpc.c
+++ b/drivers/misc/fastrpc.c
@@ -1362,7 +1362,7 @@ static int fastrpc_cb_probe(struct platf
spin_unlock_irqrestore(&cctx->lock, flags);
return -ENOSPC;
}
- sess = &cctx->session[cctx->sesscount];
+ sess = &cctx->session[cctx->sesscount++];
sess->used = false;
sess->valid = true;
sess->dev = dev;
@@ -1375,13 +1375,12 @@ static int fastrpc_cb_probe(struct platf
struct fastrpc_session_ctx *dup_sess;

for (i = 1; i < sessions; i++) {
- if (cctx->sesscount++ >= FASTRPC_MAX_SESSIONS)
+ if (cctx->sesscount >= FASTRPC_MAX_SESSIONS)
break;
- dup_sess = &cctx->session[cctx->sesscount];
+ dup_sess = &cctx->session[cctx->sesscount++];
memcpy(dup_sess, sess, sizeof(*dup_sess));
}
}
- cctx->sesscount++;
spin_unlock_irqrestore(&cctx->lock, flags);
rc = dma_set_mask(dev, DMA_BIT_MASK(32));
if (rc) {