linux-kernel - [PATCH] jfs: xattr: check invalid xattr size more strictly

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Message-ID: <20241005100658.2102-1-ancowi69@gmail.com>
Date: Sat,  5 Oct 2024 10:06:57 +0000
From: Artem Sadovnikov <ancowi69@...il.com>
To: Dave Kleikamp <shaggy@...nel.org>
Cc: Artem Sadovnikov <ancowi69@...il.com>,
	Christian Brauner <brauner@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	jfs-discussion@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org,
	lvc-project@...uxtesting.org,
	stable@...r.kernel.org
Subject: [PATCH] jfs: xattr: check invalid xattr size more strictly

Commit 7c55b78818cf ("jfs: xattr: fix buffer overflow for invalid xattr")
also addresses this issue but it only fixes it for positive values, while
ea_size is an integer type and can take negative values, e.g. in case of
a corrupted filesystem. This still breaks validation and would overflow
because of implicit conversion from int to size_t in print_hex_dump().

Fix this issue by clamping the ea_size value instead.

Found by Linux Verification Center (linuxtesting.org) with Syzkaller.

Cc: stable@...r.kernel.org
Signed-off-by: Artem Sadovnikov <ancowi69@...il.com>
---
 fs/jfs/xattr.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/jfs/xattr.c b/fs/jfs/xattr.c
index 8ef8dfc3c194..95bcbbf7359c 100644
--- a/fs/jfs/xattr.c
+++ b/fs/jfs/xattr.c
@@ -557,7 +557,7 @@ static int ea_get(struct inode *inode, struct ea_buffer *ea_buf, int min_size)
 
       size_check:
 	if (EALIST_SIZE(ea_buf->xattr) != ea_size) {
-		int size = min_t(int, EALIST_SIZE(ea_buf->xattr), ea_size);
+		int size = clamp_t(int, ea_size, 0, EALIST_SIZE(ea_buf->xattr));
 
 		printk(KERN_ERR "ea_get: invalid extended attribute\n");
 		print_hex_dump(KERN_ERR, "", DUMP_PREFIX_ADDRESS, 16, 1,
-- 
2.43.0