In the Linux kernel, the following vulnerability has been resolved:
net: deal with integer overflows in kmalloc_reserve()
Blamed commit changed: ptr = kmalloc(size); if (ptr) size = ksize(ptr);
size = kmalloc_size_roundup(size);
ptr = kmalloc(size);
This allowed various crash as reported by syzbot [1] and Kyle Zeng.
Problem is that if @size is bigger than 0x80000001, kmalloc_size_roundup(size) returns 2^32.
kmalloc_reserve() uses a 32bit variable (obj_size), so 2^32 is truncated to 0.
kmalloc(0) returns ZERO_SIZE_PTR which is not handled by skb allocations.
Following trace can be triggered if a netdev->mtu is set close to 0x7fffffff
We might in the future limit netdev->mtu to more sensible limit (like KMALLOC_MAX_SIZE).
This patch is based on a syzbot report, and also a report and tentative fix from Kyle Zeng.
[1] BUG: KASAN: user-memory-access in __build_skb_around net/core/skbuff.c:294 [inline] BUG: KASAN: user-memory-access in __alloc_skb+0x3c4/0x6e8 net/core/skbuff.c:527 Write of size 32 at addr 00000000fffffd10 by task syz-executor.4/22554
CPU: 1 PID: 22554 Comm: syz-executor.4 Not tainted 6.1.39-syzkaller #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/03/2023 Call trace: dump_backtrace+0x1c8/0x1f4 arch/arm64/kernel/stacktrace.c:279 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:286 __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x120/0x1a0 lib/dump_stack.c:106 print_report+0xe4/0x4b4 mm/kasan/report.c:398 kasan_report+0x150/0x1ac mm/kasan/report.c:495 kasan_check_range+0x264/0x2a4 mm/kasan/generic.c:189 memset+0x40/0x70 mm/kasan/shadow.c:44 __build_skb_around net/core/skbuff.c:294 [inline] __alloc_skb+0x3c4/0x6e8 net/core/skbuff.c:527 alloc_skb include/linux/skbuff.h:1316 [inline] igmpv3_newpack+0x104/0x1088 net/ipv4/igmp.c:359 add_grec+0x81c/0x1124 net/ipv4/igmp.c:534 igmpv3_send_cr net/ipv4/igmp.c:667 [inline] igmp_ifc_timer_expire+0x1b0/0x1008 net/ipv4/igmp.c:810...