memory leak in ppp_write

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: d8778f13 Merge tag 'xtensa-20190803' of git://github.com/j..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17a953d6600000
kernel config: https://syzkaller.appspot.com/x/.config?x=30cef20daf3e9977
dashboard link: https://syzkaller.appspot.com/bug?extid=d9c8bf24e56416d7ce2c
compiler: gcc (GCC) 9.0.0 20181231 (experimental)
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=16da002c600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+d9c8bf...@syzkaller.appspotmail.com

2019/08/04 10:45:32 executed programs: 5
2019/08/04 10:45:38 executed programs: 7
2019/08/04 10:45:44 executed programs: 9
2019/08/04 10:45:51 executed programs: 11
BUG: memory leak
unreferenced object 0xffff88811b943200 (size 224):
comm "syz-executor.0", pid 7102, jiffies 4294951426 (age 8.020s)
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 00 00 00 00 00 00 00 ................
backtrace:
[<00000000612bb18c>] kmemleak_alloc_recursive
include/linux/kmemleak.h:43 [inline]
[<00000000612bb18c>] slab_post_alloc_hook mm/slab.h:522 [inline]
[<00000000612bb18c>] slab_alloc_node mm/slab.c:3262 [inline]
[<00000000612bb18c>] kmem_cache_alloc_node+0x163/0x2f0 mm/slab.c:3574
[<00000000f510d7dd>] __alloc_skb+0x6e/0x210 net/core/skbuff.c:197
[<0000000064f35f9b>] alloc_skb include/linux/skbuff.h:1055 [inline]
[<0000000064f35f9b>] ppp_write+0x48/0x120
drivers/net/ppp/ppp_generic.c:502
[<000000007d5732a9>] __vfs_write+0x43/0xa0 fs/read_write.c:494
[<00000000b490138e>] vfs_write fs/read_write.c:558 [inline]
[<00000000b490138e>] vfs_write+0xee/0x210 fs/read_write.c:542
[<00000000d20d33e5>] ksys_write+0x7c/0x130 fs/read_write.c:611
[<000000007b61e45c>] __do_sys_write fs/read_write.c:623 [inline]
[<000000007b61e45c>] __se_sys_write fs/read_write.c:620 [inline]
[<000000007b61e45c>] __x64_sys_write+0x1e/0x30 fs/read_write.c:620
[<0000000067600a9b>] do_syscall_64+0x76/0x1a0
arch/x86/entry/common.c:296
[<000000007e48b83c>] entry_SYSCALL_64_after_hwframe+0x44/0xa9



---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[syzbot]

syzbot has found a reproducer for the following crash on:

HEAD commit: 6525771f Merge tag 'arc-5.3-rc7' of git://git.kernel.org/p..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16dc12a2600000
kernel config: https://syzkaller.appspot.com/x/.config?x=e6131eafb9408877

dashboard link: https://syzkaller.appspot.com/bug?extid=d9c8bf24e56416d7ce2c
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=116942de600000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1179c582600000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+d9c8bf...@syzkaller.appspotmail.com

executing program
executing program
executing program
executing program
BUG: memory leak
unreferenced object 0xffff88812a17bc00 (size 224):
comm "syz-executor673", pid 6952, jiffies 4294942888 (age 13.040s)

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 00 00 00 00 00 00 00 ................
backtrace:

[<00000000d110fff9>] kmemleak_alloc_recursive
include/linux/kmemleak.h:43 [inline]
[<00000000d110fff9>] slab_post_alloc_hook mm/slab.h:522 [inline]
[<00000000d110fff9>] slab_alloc_node mm/slab.c:3262 [inline]
[<00000000d110fff9>] kmem_cache_alloc_node+0x163/0x2f0 mm/slab.c:3574
[<000000002d616113>] __alloc_skb+0x6e/0x210 net/core/skbuff.c:197
[<000000000167fc45>] alloc_skb include/linux/skbuff.h:1055 [inline]
[<000000000167fc45>] ppp_write+0x48/0x120
drivers/net/ppp/ppp_generic.c:502
[<000000009ab42c0b>] __vfs_write+0x43/0xa0 fs/read_write.c:494
[<00000000086b2e22>] vfs_write fs/read_write.c:558 [inline]
[<00000000086b2e22>] vfs_write+0xee/0x210 fs/read_write.c:542
[<00000000a2b70ef9>] ksys_write+0x7c/0x130 fs/read_write.c:611
[<00000000ce5e0fdd>] __do_sys_write fs/read_write.c:623 [inline]
[<00000000ce5e0fdd>] __se_sys_write fs/read_write.c:620 [inline]
[<00000000ce5e0fdd>] __x64_sys_write+0x1e/0x30 fs/read_write.c:620
[<00000000d9d7b370>] do_syscall_64+0x76/0x1a0
arch/x86/entry/common.c:296
[<0000000006e6d506>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

BUG: memory leak
unreferenced object 0xffff888121203900 (size 224):
comm "syz-executor673", pid 6965, jiffies 4294943430 (age 7.620s)

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 00 00 00 00 00 00 00 ................
backtrace:

[<00000000d110fff9>] kmemleak_alloc_recursive
include/linux/kmemleak.h:43 [inline]
[<00000000d110fff9>] slab_post_alloc_hook mm/slab.h:522 [inline]
[<00000000d110fff9>] slab_alloc_node mm/slab.c:3262 [inline]
[<00000000d110fff9>] kmem_cache_alloc_node+0x163/0x2f0 mm/slab.c:3574
[<000000002d616113>] __alloc_skb+0x6e/0x210 net/core/skbuff.c:197
[<000000000167fc45>] alloc_skb include/linux/skbuff.h:1055 [inline]
[<000000000167fc45>] ppp_write+0x48/0x120
drivers/net/ppp/ppp_generic.c:502
[<000000009ab42c0b>] __vfs_write+0x43/0xa0 fs/read_write.c:494
[<00000000086b2e22>] vfs_write fs/read_write.c:558 [inline]
[<00000000086b2e22>] vfs_write+0xee/0x210 fs/read_write.c:542
[<00000000a2b70ef9>] ksys_write+0x7c/0x130 fs/read_write.c:611
[<00000000ce5e0fdd>] __do_sys_write fs/read_write.c:623 [inline]
[<00000000ce5e0fdd>] __se_sys_write fs/read_write.c:620 [inline]
[<00000000ce5e0fdd>] __x64_sys_write+0x1e/0x30 fs/read_write.c:620
[<00000000d9d7b370>] do_syscall_64+0x76/0x1a0
arch/x86/entry/common.c:296
[<0000000006e6d506>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

BUG: memory leak
unreferenced object 0xffff88811d0cf800 (size 512):
comm "syz-executor673", pid 6965, jiffies 4294943430 (age 7.620s)

hex dump (first 32 bytes):

06 00 00 00 05 00 00 00 40 00 00 00 00 00 00 00 ........@.......
40 00 40 00 00 00 00 00 40 00 40 00 00 00 00 00 @.@.....@.@.....
backtrace:
[<00000000b9629d4c>] kmemleak_alloc_recursive
include/linux/kmemleak.h:43 [inline]
[<00000000b9629d4c>] slab_post_alloc_hook mm/slab.h:522 [inline]
[<00000000b9629d4c>] slab_alloc_node mm/slab.c:3262 [inline]
[<00000000b9629d4c>] kmem_cache_alloc_node_trace+0x161/0x2f0
mm/slab.c:3592
[<00000000a9b92035>] __do_kmalloc_node mm/slab.c:3614 [inline]
[<00000000a9b92035>] __kmalloc_node_track_caller+0x38/0x50
mm/slab.c:3629
[<00000000fad050db>] __kmalloc_reserve.isra.0+0x40/0xb0
net/core/skbuff.c:141
[<00000000a1025904>] __alloc_skb+0xa0/0x210 net/core/skbuff.c:209
[<000000000167fc45>] alloc_skb include/linux/skbuff.h:1055 [inline]
[<000000000167fc45>] ppp_write+0x48/0x120
drivers/net/ppp/ppp_generic.c:502
[<000000009ab42c0b>] __vfs_write+0x43/0xa0 fs/read_write.c:494
[<00000000086b2e22>] vfs_write fs/read_write.c:558 [inline]
[<00000000086b2e22>] vfs_write+0xee/0x210 fs/read_write.c:542
[<00000000a2b70ef9>] ksys_write+0x7c/0x130 fs/read_write.c:611
[<00000000ce5e0fdd>] __do_sys_write fs/read_write.c:623 [inline]
[<00000000ce5e0fdd>] __se_sys_write fs/read_write.c:620 [inline]
[<00000000ce5e0fdd>] __x64_sys_write+0x1e/0x30 fs/read_write.c:620
[<00000000d9d7b370>] do_syscall_64+0x76/0x1a0
arch/x86/entry/common.c:296
[<0000000006e6d506>] entry_SYSCALL_64_after_hwframe+0x44/0xa9

[Takeshi Misawa]

#syz test: https://github.com/google/kasan.git 6525771f

[syzbot]

Hello,

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

Reported-and-tested-by:
syzbot+d9c8bf...@syzkaller.appspotmail.com

Tested on:

commit: 6525771f Merge tag 'arc-5.3-rc7' of git://git.kernel.org/p..

git tree: https://github.com/google/kasan.git

kernel config: https://syzkaller.appspot.com/x/.config?x=e6131eafb9408877
dashboard link: https://syzkaller.appspot.com/bug?extid=d9c8bf24e56416d7ce2c
compiler: gcc (GCC) 9.0.0 20181231 (experimental)

patch: https://syzkaller.appspot.com/x/patch.diff?x=12610ef1600000

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