linux-kernel - [PATCH] jfs: fix slab-out-of-bounds read in ea

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20250213002025.6602-1-qasdev00@gmail.com>
Date: Thu, 13 Feb 2025 00:20:25 +0000
From: Qasim Ijaz <qasdev00@...il.com>
To: shaggy@...nel.org,
	zhaomengmeng@...inos.cn,
	llfamsec@...il.com,
	gregkh@...uxfoundation.org,
	ancowi69@...il.com
Cc: jfs-discussion@...ts.sourceforge.net,
	linux-kernel@...r.kernel.org,
	syzbot <syzbot+4e6e7e4279d046613bc5@...kaller.appspotmail.com>
Subject: [PATCH] jfs: fix slab-out-of-bounds read in ea_get()

During the "size_check" label in ea_get(), the code checks if the extended 
attribute list (xattr) size matches ea_size. If not, it logs 
"ea_get: invalid extended attribute" and calls print_hex_dump().

Here, EALIST_SIZE(ea_buf->xattr) returns 4110417968, which exceeds 
INT_MAX (2,147,483,647). Then ea_size is clamped:

	int size = clamp_t(int, ea_size, 0, EALIST_SIZE(ea_buf->xattr));

Although clamp_t aims to bound ea_size between 0 and 4110417968, the upper 
limit is treated as an int, causing an overflow above 2^31 - 1. This leads 
"size" to wrap around and become negative (-184549328).

The "size" is then passed to print_hex_dump() (called "len" in 
print_hex_dump()), it is passed as type size_t (an unsigned 
type), this is then stored inside a variable called 
"int remaining", which is then assigned to "int linelen" which 
is then passed to hex_dump_to_buffer(). In print_hex_dump() 
the for loop, iterates through 0 to len-1, where len is 
18446744073525002176, calling hex_dump_to_buffer() 
on each iteration:

	for (i = 0; i < len; i += rowsize) {
		linelen = min(remaining, rowsize);
		remaining -= rowsize;

		hex_dump_to_buffer(ptr + i, linelen, rowsize, groupsize,
				   linebuf, sizeof(linebuf), ascii);

		...
	}

The expected stopping condition (i < len) is effectively broken 
since len is corrupted and very large. This eventually leads to 
the "ptr+i" being passed to hex_dump_to_buffer() to get closer 
to the end of the actual bounds of "ptr", eventually an out of 
bounds access is done in hex_dump_to_buffer() in the following 
for loop:

	for (j = 0; j < len; j++) {
			if (linebuflen < lx + 2)
				goto overflow2;
			ch = ptr[j];
		...
	}

To fix this we should validate "EALIST_SIZE(ea_buf->xattr)" 
before it is utilised.

Reported-by: syzbot <syzbot+4e6e7e4279d046613bc5@...kaller.appspotmail.com>
Tested-by: syzbot <syzbot+4e6e7e4279d046613bc5@...kaller.appspotmail.com>
Closes: https://syzkaller.appspot.com/bug?extid=4e6e7e4279d046613bc5
Fixes: d9f9d96136cb ("jfs: xattr: check invalid xattr size more strictly")
Signed-off-by: Qasim Ijaz <qasdev00@...il.com>
---
 fs/jfs/xattr.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/fs/jfs/xattr.c b/fs/jfs/xattr.c
index 24afbae87225..7575c51cce9b 100644
--- a/fs/jfs/xattr.c
+++ b/fs/jfs/xattr.c
@@ -559,11 +555,16 @@ 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 = 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,
-				     ea_buf->xattr, size, 1);
+		if (unlikely(EALIST_SIZE(ea_buf->xattr) > INT_MAX)) {
+			printk(KERN_ERR "ea_get: extended attribute size too large: %u > INT_MAX\n",
+			       EALIST_SIZE(ea_buf->xattr));
+		} else {
+			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,
+				       ea_buf->xattr, size, 1);
+		}
 		ea_release(inode, ea_buf);
 		rc = -EIO;
 		goto clean_up;
-- 
2.39.5