linux-kernel - [PATCH v2] block: fix potential invalid pointer dereference in blk_add

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Message-ID: <20240911132954.5874-1-riyandhiman14@gmail.com>
Date: Wed, 11 Sep 2024 18:59:54 +0530
From: Riyan Dhiman <riyandhiman14@...il.com>
To: axboe@...nel.dk
Cc: hch@....de,
	linux-block@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Riyan Dhiman <riyandhiman14@...il.com>
Subject: [PATCH v2] block: fix potential invalid pointer dereference in blk_add_partition

The blk_add_partition() function initially used a single if-condition
(IS_ERR(part)) to check for errors when adding a partition. This was
modified to handle the specific case of -ENXIO separately, allowing the
function to proceed without logging the error in this case. However,
this change unintentionally left a path where md_autodetect_dev()
could be called without confirming that part is a valid pointer.

This commit separates the error handling logic by splitting the
initial if-condition, improving code readability and handling specific
error scenarios explicitly. The function now distinguishes the general
error case from -ENXIO without altering the existing behavior of
md_autodetect_dev() calls.

Fixes: b72053072c0b (block: allow partitions on host aware zone devices)
Signed-off-by: Riyan Dhiman <riyandhiman14@...il.com>
---
Compile tested only.
V2 -> removed line between Fixes tag and Signed-off and cc commit author

 block/partitions/core.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/block/partitions/core.c b/block/partitions/core.c
index ab76e64f0f6c..5bd7a603092e 100644
--- a/block/partitions/core.c
+++ b/block/partitions/core.c
@@ -555,9 +555,11 @@ static bool blk_add_partition(struct gendisk *disk,

 	part = add_partition(disk, p, from, size, state->parts[p].flags,
 			     &state->parts[p].info);
-	if (IS_ERR(part) && PTR_ERR(part) != -ENXIO) {
-		printk(KERN_ERR " %s: p%d could not be added: %pe\n",
-		       disk->disk_name, p, part);
+	if (IS_ERR(part)) {
+		if (PTR_ERR(part) != -ENXIO) {
+			printk(KERN_ERR " %s: p%d could not be added: %pe\n",
+			       disk->disk_name, p, part);
+		}
 		return true;
 	}

-- 
2.46.0