File 0042-fs-squashfs-sqfs_read-Prevent-arbit.patch of Package u-boot.25329

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File 0042-fs-squashfs-sqfs_read-Prevent-arbit.patch of Package u-boot.25329

From 77cf75780769cf357fed83e4df5adcb0c5f38565 Mon Sep 17 00:00:00 2001
From: Miquel Raynal <miquel.raynal@bootlin.com>
Date: Thu, 9 Jun 2022 16:02:06 +0200
Subject: [PATCH] fs/squashfs: sqfs_read: Prevent arbitrary code execution

Following Jincheng's report, an out-of-band write leading to arbitrary
code execution is possible because on one side the squashfs logic
accepts directory names up to 65535 bytes (u16), while U-Boot fs logic
accepts directory names up to 255 bytes long.

Prevent such an exploit from happening by capping directory name sizes
to 255. Use a define for this purpose so that developers can link the
limitation to its source and eventually kill it some day by dynamically
allocating this array (if ever desired).

Link: https://lore.kernel.org/all/CALO=DHFB+yBoXxVr5KcsK0iFdg+e7ywko4-e+72kjbcS8JBfPw@mail.gmail.com
Reported-by: Jincheng Wang <jc.w4ng@gmail.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Tested-by: Jincheng Wang <jc.w4ng@gmail.com>
(cherry picked from commit 2ac0baab4aff1a0b45067d0b62f00c15f4e86856)
Signed-off-by: Matthias Brugger <mbrugger@suse.com>
---
 fs/squashfs/sqfs.c | 8 +++++---
 include/fs.h       | 4 +++-
 2 files changed, 8 insertions(+), 4 deletions(-)

diff --git a/fs/squashfs/sqfs.c b/fs/squashfs/sqfs.c
index e6e8b06061..49f815256f 100644
--- a/fs/squashfs/sqfs.c
+++ b/fs/squashfs/sqfs.c
@@ -975,6 +975,7 @@ int sqfs_readdir(struct fs_dir_stream *fs_dirs, struct fs_dirent **dentp)
 	int i_number, offset = 0, ret;
 	struct fs_dirent *dent;
 	unsigned char *ipos;
+	u16 name_size;
 
 	dirs = (struct squashfs_dir_stream *)fs_dirs;
 	if (!dirs->size) {
@@ -1057,9 +1058,10 @@ int sqfs_readdir(struct fs_dir_stream *fs_dirs, struct fs_dirent **dentp)
 		return -SQFS_STOP_READDIR;
 	}
 
-	/* Set entry name */
-	strncpy(dent->name, dirs->entry->name, dirs->entry->name_size + 1);
-	dent->name[dirs->entry->name_size + 1] = '\0';
+	/* Set entry name (capped at FS_DIRENT_NAME_LEN which is a U-Boot limitation) */
+	name_size = min_t(u16, dirs->entry->name_size + 1, FS_DIRENT_NAME_LEN - 1);
+	strncpy(dent->name, dirs->entry->name, name_size);
+	dent->name[name_size] = '\0';
 
 	offset = dirs->entry->name_size + 1 + SQFS_ENTRY_BASE_LENGTH;
 	dirs->entry_count--;
diff --git a/include/fs.h b/include/fs.h
index 0794b50d10..fb44d17c53 100644
--- a/include/fs.h
+++ b/include/fs.h
@@ -160,6 +160,8 @@ int fs_write(const char *filename, ulong addr, loff_t offset, loff_t len,
 #define FS_DT_REG  8         /* regular file */
 #define FS_DT_LNK  10        /* symbolic link */
 
+#define FS_DIRENT_NAME_LEN 256
+
 /*
  * A directory entry, returned by fs_readdir().  Returns information
  * about the file/directory at the current directory entry position.
@@ -167,7 +169,7 @@ int fs_write(const char *filename, ulong addr, loff_t offset, loff_t len,
 struct fs_dirent {
 	unsigned type;       /* one of FS_DT_x (not a mask) */
 	loff_t size;         /* size in bytes */
-	char name[256];
+	char name[FS_DIRENT_NAME_LEN];
 };
 
 /* Note: fs_dir_stream should be treated as opaque to the user of fs layer */

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