4.4-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ Upstream commit e5dcc0c3223c45c94100f05f28d8ef814db3d82c ]
rose_write_internal() uses a temp buffer of 100 bytes, but a manual inspection showed that given arbitrary input, rose_create_facilities() can fill up to 110 bytes.
Lets use a tailroom of 256 bytes for peace of mind, and remove the bounce buffer : we can simply allocate a big enough skb and adjust its length as needed.
syzbot report :
BUG: KASAN: stack-out-of-bounds in memcpy include/linux/string.h:352 [inline] BUG: KASAN: stack-out-of-bounds in rose_create_facilities net/rose/rose_subr.c:521 [inline] BUG: KASAN: stack-out-of-bounds in rose_write_internal+0x597/0x15d0 net/rose/rose_subr.c:116 Write of size 7 at addr ffff88808b1ffbef by task syz-executor.0/24854
CPU: 0 PID: 24854 Comm: syz-executor.0 Not tainted 5.0.0+ #97 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011 Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x172/0x1f0 lib/dump_stack.c:113 print_address_description.cold+0x7c/0x20d mm/kasan/report.c:187 kasan_report.cold+0x1b/0x40 mm/kasan/report.c:317 check_memory_region_inline mm/kasan/generic.c:185 [inline] check_memory_region+0x123/0x190 mm/kasan/generic.c:191 memcpy+0x38/0x50 mm/kasan/common.c:131 memcpy include/linux/string.h:352 [inline] rose_create_facilities net/rose/rose_subr.c:521 [inline] rose_write_internal+0x597/0x15d0 net/rose/rose_subr.c:116 rose_connect+0x7cb/0x1510 net/rose/af_rose.c:826 __sys_connect+0x266/0x330 net/socket.c:1685 __do_sys_connect net/socket.c:1696 [inline] __se_sys_connect net/socket.c:1693 [inline] __x64_sys_connect+0x73/0xb0 net/socket.c:1693 do_syscall_64+0x103/0x610 arch/x86/entry/common.c:290 entry_SYSCALL_64_after_hwframe+0x49/0xbe RIP: 0033:0x458079 Code: ad b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 7b b8 fb ff c3 66 2e 0f 1f 84 00 00 00 00 RSP: 002b:00007f47b8d9dc78 EFLAGS: 00000246 ORIG_RAX: 000000000000002a RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 0000000000458079 RDX: 000000000000001c RSI: 0000000020000040 RDI: 0000000000000004 RBP: 000000000073bf00 R08: 0000000000000000 R09: 0000000000000000 R10: 0000000000000000 R11: 0000000000000246 R12: 00007f47b8d9e6d4 R13: 00000000004be4a4 R14: 00000000004ceca8 R15: 00000000ffffffff
The buggy address belongs to the page: page:ffffea00022c7fc0 count:0 mapcount:0 mapping:0000000000000000 index:0x0 flags: 0x1fffc0000000000() raw: 01fffc0000000000 0000000000000000 ffffffff022c0101 0000000000000000 raw: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 page dumped because: kasan: bad access detected
Memory state around the buggy address: ffff88808b1ffa80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ffff88808b1ffb00: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 00 00 03
ffff88808b1ffb80: f2 f2 00 00 00 00 00 00 00 00 00 00 00 00 04 f3
^ ffff88808b1ffc00: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00 ffff88808b1ffc80: 00 00 00 00 00 00 00 f1 f1 f1 f1 f1 f1 01 f2 01
Signed-off-by: Eric Dumazet edumazet@google.com Reported-by: syzbot syzkaller@googlegroups.com Signed-off-by: David S. Miller davem@davemloft.net Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/rose/rose_subr.c | 21 ++++++++++++--------- 1 file changed, 12 insertions(+), 9 deletions(-)
--- a/net/rose/rose_subr.c +++ b/net/rose/rose_subr.c @@ -105,16 +105,17 @@ void rose_write_internal(struct sock *sk struct sk_buff *skb; unsigned char *dptr; unsigned char lci1, lci2; - char buffer[100]; - int len, faclen = 0; + int maxfaclen = 0; + int len, faclen; + int reserve;
- len = AX25_BPQ_HEADER_LEN + AX25_MAX_HEADER_LEN + ROSE_MIN_LEN + 1; + reserve = AX25_BPQ_HEADER_LEN + AX25_MAX_HEADER_LEN + 1; + len = ROSE_MIN_LEN;
switch (frametype) { case ROSE_CALL_REQUEST: len += 1 + ROSE_ADDR_LEN + ROSE_ADDR_LEN; - faclen = rose_create_facilities(buffer, rose); - len += faclen; + maxfaclen = 256; break; case ROSE_CALL_ACCEPTED: case ROSE_CLEAR_REQUEST: @@ -123,15 +124,16 @@ void rose_write_internal(struct sock *sk break; }
- if ((skb = alloc_skb(len, GFP_ATOMIC)) == NULL) + skb = alloc_skb(reserve + len + maxfaclen, GFP_ATOMIC); + if (!skb) return;
/* * Space for AX.25 header and PID. */ - skb_reserve(skb, AX25_BPQ_HEADER_LEN + AX25_MAX_HEADER_LEN + 1); + skb_reserve(skb, reserve);
- dptr = skb_put(skb, skb_tailroom(skb)); + dptr = skb_put(skb, len);
lci1 = (rose->lci >> 8) & 0x0F; lci2 = (rose->lci >> 0) & 0xFF; @@ -146,7 +148,8 @@ void rose_write_internal(struct sock *sk dptr += ROSE_ADDR_LEN; memcpy(dptr, &rose->source_addr, ROSE_ADDR_LEN); dptr += ROSE_ADDR_LEN; - memcpy(dptr, buffer, faclen); + faclen = rose_create_facilities(dptr, rose); + skb_put(skb, faclen); dptr += faclen; break;