FAILED: patch "[PATCH] usb: gadget: f_mass_storage: fix null pointer dereference in" failed to apply to 6.12-stable tree

The patch below does not apply to the 6.12-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.12.y
git checkout FETCH_HEAD
git cherry-pick -x 2c0f5ca48674a5b5f9fa4a9c3325aa48053af0bc
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026090850-exonerate-dumpster-494a@gregkh' --subject-prefix 'PATCH 6.12.y' 'HEAD^..'

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2c0f5ca48674a5b5f9fa4a9c3325aa48053af0bc Mon Sep 17 00:00:00 2001
From: Jeffin Philip <[email protected]>
Date: Tue, 18 Aug 2026 09:29:04 +0530
Subject: [PATCH] usb: gadget: f_mass_storage: fix null pointer dereference in
fsg_common_set_num_buffers()

Previously fsg_num_buffers_validate() was removed as it was not necessary due to Kconfig setting the limits for n from 2 to 256 with default as 2. However, setting the page content in such a way that kstrtou8() reflects n value as either 0 or 1 bypasses these restrictions leading to a null pointer dereference if n is 0. Fix this by adding a check for n < 2 and returning -EINVAL if n is either 0 or 1 consistent with Kconfig logic.

index 1a0fbc808ee2..fc4818fb2a8b 100644
@@ -2747,6 +2747,9 @@ int fsg_common_set_num_buffers(struct fsg_common *common, unsigned int n)
 	struct fsg_buffhd *bh, *buffhds;
 	int i;
 
+	if (n < 2)
+		return -EINVAL;
+
 	buffhds = kzalloc_objs(*buffhds, n);
 	if (!buffhds)
 		return -ENOMEM;

From: Jeffin Philip <[email protected]>

[ Upstream commit 2c0f5ca48674a5b5f9fa4a9c3325aa48053af0bc ]

Previously fsg_num_buffers_validate() was removed as it was not necessary due to Kconfig setting the limits for n from 2 to 256 with default as 2. However, setting the page content in such a way that kstrtou8() reflects n value as either 0 or 1 bypasses these restrictions leading to a null pointer dereference if n is 0. Fix this by adding a check for n < 2 and returning -EINVAL if n is either 0 or 1 consistent with Kconfig logic.

---
 drivers/usb/gadget/function/f_mass_storage.c | 3 +++
 1 file changed, 3 insertions(+)

index 74cb7e57a197c..341cb3861a13f 100644
@@ -2748,6 +2748,9 @@ int fsg_common_set_num_buffers(struct fsg_common *common, unsigned int n)
 	struct fsg_buffhd *bh, *buffhds;
 	int i;
 
+	if (n < 2)
+		return -EINVAL;
+
 	buffhds = kcalloc(n, sizeof(*buffhds), GFP_KERNEL);
 	if (!buffhds)
 		return -ENOMEM;

2.53.0