linux-kernel - [PATCH][next] drm/i915: fix size_t greater or equal to zero comparison

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Message-Id: <20201002170354.94627-1-colin.king@canonical.com>
Date:   Fri,  2 Oct 2020 18:03:54 +0100
From:   Colin King <colin.king@...onical.com>
To:     Jani Nikula <jani.nikula@...ux.intel.com>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] drm/i915: fix size_t greater or equal to zero comparison

From: Colin Ian King <colin.king@...onical.com>

Currently the check that the unsigned size_t variable i is >= 0
is always true because the unsigned variable will never be negative,
causing the loop to run forever.  Fix this by changing the
pre-decrement check to a zero check on i followed by a decrement of i.

Addresses-Coverity: ("Unsigned compared against 0")
Fixes: 400b65cb5acb ("drm/i915: use vmap in shmem_pin_map")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 drivers/gpu/drm/i915/gt/shmem_utils.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/shmem_utils.c b/drivers/gpu/drm/i915/gt/shmem_utils.c
index f011ea42487e..30cc56fa191f 100644
--- a/drivers/gpu/drm/i915/gt/shmem_utils.c
+++ b/drivers/gpu/drm/i915/gt/shmem_utils.c
@@ -73,7 +73,7 @@ void *shmem_pin_map(struct file *file)
 	mapping_set_unevictable(file->f_mapping);
 	return vaddr;
 err_page:
-	while (--i >= 0)
+	while (i--)
 		put_page(pages[i]);
 	kvfree(pages);
 	return NULL;
-- 
2.27.0