[syzbot] [hams?] memory leak in nr_sendmsg

[syzbot] [hams?] memory leak in nr_sendmsg

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    ac3fd01e4c1e Linux 6.18-rc7
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=117ab612580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f30cc590c4f6da44
dashboard link: https://syzkaller.appspot.com/bug?extid=d7abc36bbbb6d7d40b58
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13dd8f42580000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=115bc612580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/308a482d95ee/disk-ac3fd01e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/ed239243510b/vmlinux-ac3fd01e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/dd12243dca3d/bzImage-ac3fd01e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+d7abc36bbbb6d7d40b58@syzkaller.appspotmail.com

BUG: memory leak
unreferenced object 0xffff888129f35500 (size 240):
  comm "syz.0.17", pid 6119, jiffies 4294944652
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ................
    00 00 00 00 00 00 00 00 00 10 52 28 81 88 ff ff  ..........R(....
  backtrace (crc 1456a3e4):
    kmemleak_alloc_recursive include/linux/kmemleak.h:44 [inline]
    slab_post_alloc_hook mm/slub.c:4983 [inline]
    slab_alloc_node mm/slub.c:5288 [inline]
    kmem_cache_alloc_node_noprof+0x36f/0x5e0 mm/slub.c:5340
    __alloc_skb+0x203/0x240 net/core/skbuff.c:660
    alloc_skb include/linux/skbuff.h:1383 [inline]
    alloc_skb_with_frags+0x69/0x3f0 net/core/skbuff.c:6671
    sock_alloc_send_pskb+0x379/0x3e0 net/core/sock.c:2965
    sock_alloc_send_skb include/net/sock.h:1859 [inline]
    nr_sendmsg+0x287/0x450 net/netrom/af_netrom.c:1105
    sock_sendmsg_nosec net/socket.c:727 [inline]
    __sock_sendmsg net/socket.c:742 [inline]
    sock_write_iter+0x293/0x2a0 net/socket.c:1195
    new_sync_write fs/read_write.c:593 [inline]
    vfs_write+0x45d/0x710 fs/read_write.c:686
    ksys_write+0x143/0x170 fs/read_write.c:738
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xfa0 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

BUG: memory leak
unreferenced object 0xffff8881112c0000 (size 65536):
  comm "syz.0.17", pid 6119, jiffies 4294944652
  hex dump (first 32 bytes):
    00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 01  ................
    01 00 00 05 02 98 92 9c aa b0 40 02 00 00 00 00  ..........@.....
  backtrace (crc 75262837):
    ___kmalloc_large_node+0xc1/0x100 mm/slub.c:5604
    __kmalloc_large_node_noprof+0x18/0xa0 mm/slub.c:5622
    __do_kmalloc_node mm/slub.c:5638 [inline]
    __kmalloc_node_track_caller_noprof+0x412/0x6b0 mm/slub.c:5759
    kmalloc_reserve+0x96/0x180 net/core/skbuff.c:601
    __alloc_skb+0xd4/0x240 net/core/skbuff.c:670
    alloc_skb include/linux/skbuff.h:1383 [inline]
    alloc_skb_with_frags+0x69/0x3f0 net/core/skbuff.c:6671
    sock_alloc_send_pskb+0x379/0x3e0 net/core/sock.c:2965
    sock_alloc_send_skb include/net/sock.h:1859 [inline]
    nr_sendmsg+0x287/0x450 net/netrom/af_netrom.c:1105
    sock_sendmsg_nosec net/socket.c:727 [inline]
    __sock_sendmsg net/socket.c:742 [inline]
    sock_write_iter+0x293/0x2a0 net/socket.c:1195
    new_sync_write fs/read_write.c:593 [inline]
    vfs_write+0x45d/0x710 fs/read_write.c:686
    ksys_write+0x143/0x170 fs/read_write.c:738
    do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
    do_syscall_64+0xa4/0xfa0 arch/x86/entry/syscall_64.c:94
    entry_SYSCALL_64_after_hwframe+0x77/0x7f

connection error: failed to recv *flatrpc.ExecutorMessageRawT: EOF


---
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Forwarded: [PATCH] net: netrom: fix memory leak in nr_output()

[syzbot]

For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.

***

Subject: [PATCH] net: netrom: fix memory leak in nr_output()
Author: kartikey406@gmail.com

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master


When nr_output() fragments a large packet, it calls sock_alloc_send_skb()
in a loop to allocate skbs for each fragment. If this allocation fails,
the function returns without freeing the original skb that was passed in,
causing a memory leak.

Add the missing kfree_skb() call before returning on allocation failure.

Reported-by: syzbot+d7abc36bbbb6d7d40b58@syzkaller.appspotmail.com
Closes: https://syzkaller.appspot.com/bug?extid=d7abc36bbbb6d7d40b58
Signed-off-by: Deepanshu Kartikey <kartikey406@gmail.com>
---
 net/netrom/nr_out.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/netrom/nr_out.c b/net/netrom/nr_out.c
index 5e531394a724..2b3cbceb0b52 100644
--- a/net/netrom/nr_out.c
+++ b/net/netrom/nr_out.c
@@ -43,8 +43,10 @@ void nr_output(struct sock *sk, struct sk_buff *skb)
 		frontlen = skb_headroom(skb);
 
 		while (skb->len > 0) {
-			if ((skbn = sock_alloc_send_skb(sk, frontlen + NR_MAX_PACKET_SIZE, 0, &err)) == NULL)
+			if ((skbn = sock_alloc_send_skb(sk, frontlen + NR_MAX_PACKET_SIZE, 0, &err)) == NULL) {
+				kfree_skb(skb);
 				return;
+			}
 
 			skb_reserve(skbn, frontlen);
 
-- 
2.43.0

Re: [syzbot] [hams?] memory leak in nr_sendmsg

[Wang Liang]

#syz test

diff --git a/net/netrom/nr_out.c b/net/netrom/nr_out.c
index 5e531394a724..2b3cbceb0b52 100644
--- a/net/netrom/nr_out.c
+++ b/net/netrom/nr_out.c
@@ -43,8 +43,10 @@ void nr_output(struct sock *sk, struct sk_buff *skb)
 		frontlen = skb_headroom(skb);
 
 		while (skb->len > 0) {
-			if ((skbn = sock_alloc_send_skb(sk, frontlen + NR_MAX_PACKET_SIZE, 0, &err)) == NULL)
+			if ((skbn = sock_alloc_send_skb(sk, frontlen + NR_MAX_PACKET_SIZE, 0, &err)) == NULL) {
+				kfree_skb(skb);
 				return;
+			}
 
 			skb_reserve(skbn, frontlen);
 
-- 
2.34.1

Re: [syzbot] [hams?] memory leak in nr_sendmsg

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger any issue:

Reported-by: syzbot+d7abc36bbbb6d7d40b58@syzkaller.appspotmail.com
Tested-by: syzbot+d7abc36bbbb6d7d40b58@syzkaller.appspotmail.com

Tested on:

commit:         19eef1d9 afs: Fix uninit var in afs_alloc_anon_key()
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14a88112580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f30cc590c4f6da44
dashboard link: https://syzkaller.appspot.com/bug?extid=d7abc36bbbb6d7d40b58
compiler:       gcc (Debian 12.2.0-14+deb12u1) 12.2.0, GNU ld (GNU Binutils for Debian) 2.40
patch:          https://syzkaller.appspot.com/x/patch.diff?x=13a9be92580000

Note: testing is done by a robot and is best-effort only.