linux-kernel - [PATCH] scsi: aacraid: Prevent premature freeing and improve memory allocation checks for fsa

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Message-ID: <20240903171911.9197-1-riyandhiman14@gmail.com>
Date: Tue,  3 Sep 2024 22:49:11 +0530
From: Riyan Dhiman <riyandhiman14@...il.com>
To: aacraid@...rosemi.com,
	James.Bottomley@...senPartnership.com,
	martin.petersen@...cle.com
Cc: linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Riyan Dhiman <riyandhiman14@...il.com>
Subject: [PATCH] scsi: aacraid: Prevent premature freeing and improve memory allocation checks for fsa_dev

Refactor the allocation and freeing sequence of `fsa_dev` to ensure
that memory is not prematurely freed, which could lead to use-after-free errors
or undefined behavior.

Changes:
- Modified the order of memory operations by allocating new memory for fsa_dev
  first and checking for success before freeing the old fsa_dev pointer.
- Updated the error handling to ensure -ENOMEM is returned if allocation fails,
  preserving the existing valid memory.

Signed-off-by: Riyan Dhiman <riyandhiman14@...il.com>
---
 drivers/scsi/aacraid/aachba.c | 14 +++++---------
 1 file changed, 5 insertions(+), 9 deletions(-)

diff --git a/drivers/scsi/aacraid/aachba.c b/drivers/scsi/aacraid/aachba.c
index b22857c6f3f4..f3fc9b622aee 100644
--- a/drivers/scsi/aacraid/aachba.c
+++ b/drivers/scsi/aacraid/aachba.c
@@ -490,18 +490,14 @@ int aac_get_containers(struct aac_dev *dev)
 	if (dev->fsa_dev == NULL ||
 		dev->maximum_num_containers != maximum_num_containers) {
 
-		fsa_dev_ptr = dev->fsa_dev;
-
-		dev->fsa_dev = kcalloc(maximum_num_containers,
+		fsa_dev_ptr = kcalloc(maximum_num_containers,
 					sizeof(*fsa_dev_ptr), GFP_KERNEL);
-
-		kfree(fsa_dev_ptr);
-		fsa_dev_ptr = NULL;
-
-
-		if (!dev->fsa_dev)
+		if(!fsa_dev_ptr)
 			return -ENOMEM;
 
+		kfree(dev->fsa_dev);
+		dev->fsa_dev = fsa_dev_ptr;
+
 		dev->maximum_num_containers = maximum_num_containers;
 	}
 	for (index = 0; index < dev->maximum_num_containers; index++) {
-- 
2.46.0