[PATCH v3 1/6] qnx6: validate di_filelevels in qnx6_iget() before accessing level pointers

[Hui Peng <benquike@gmail.com>]

In qnx6_iget(), raw_inode->di_filelevels is read directly from the disk
image and stored into qnx6_inode->di_filelevels without checking if it
exceeds QNX6_PTR_MAX_LEVELS (3). If a corrupted disk image contains
di_filelevels > 3, subsequent file operations using qnx6_block_map()
access qnx6_inode->di_ptr[] past its array bound, causing out-of-bounds
reads and memory corruption.

Validate raw_inode->di_filelevels <= QNX6_PTR_MAX_LEVELS in qnx6_iget()
and return -EIO on corrupt inodes.

Fixes: 5d026c724220 ("fs: initial qnx6fs addition")
Cc: stable@vger.kernel.org
Tested-by: Matthias Goergens <matthias.goergens@gmail.com>
Reviewed-by: Matthias Goergens <matthias.goergens@gmail.com>
Assisted-by: LLM
Signed-off-by: Hui Peng <benquike@gmail.com>
---
Changes in v3:
- Add Tested-by and Reviewed-by tags from Matthias Goergens.
- Update Fixes: tag SHA to 5d026c724220 ("fs: initial qnx6fs addition").

Changes in v2:
- Split out as patch 1/6 as requested by maintainers.

 fs/qnx6/inode.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/qnx6/inode.c b/fs/qnx6/inode.c
index a15c4de4f794..e1981e4ae47d 100644
--- a/fs/qnx6/inode.c
+++ b/fs/qnx6/inode.c
@@ -547,6 +547,11 @@ struct inode *qnx6_iget(struct super_block *sb, unsigned ino)
 
 	qnx6_inode->di_filelevels = raw_inode->di_filelevels;
 	qnx6_inode->di_status = raw_inode->di_status;
+	if (qnx6_inode->di_filelevels > QNX6_PTR_MAX_LEVELS) {
+		pr_err("invalid di_filelevels %u\n", qnx6_inode->di_filelevels);
+		iget_failed(inode);
+		return ERR_PTR(-EIO);
+	}
 	if (S_ISDIR(inode->i_mode) || S_ISREG(inode->i_mode)) {
 		memcpy(qnx6_inode->di_ptr, raw_inode->di_ptr,
 		       sizeof(qnx6_inode->di_ptr));
-- 
2.55.0.1082.g2b9226bbc0-goog