CVE-2024-56615: bpf: fix OOB devmap writes when deleting elements

In the Linux kernel, the following vulnerability has been resolved:

bpf: fix OOB devmap writes when deleting elements

Jordy reported issue against XSKMAP which also applies to DEVMAP - the index used for accessing map entry, due to being a signed integer, causes the OOB writes. Fix is simple as changing the type from int to u32, however, when compared to XSKMAP case, one more thing needs to be addressed.

When map is released from system via devmapfree(), we iterate through all of the entries and an iterator variable is also an int, which implies OOB accesses. Again, change it to be u32.

Example splat below:

[ 160.724676] BUG: unable to handle page fault for address: ffffc8fc2c001000 [ 160.731662] #PF: supervisor read access in kernel mode [ 160.736876] #PF: errorcode(0x0000) - not-present page [ 160.742095] PGD 0 P4D 0 [ 160.744678] Oops: Oops: 0000 [#1] PREEMPT SMP [ 160.749106] CPU: 1 UID: 0 PID: 520 Comm: kworker/u145:12 Not tainted 6.12.0-rc1+ #487 [ 160.757050] Hardware name: Intel Corporation S2600WFT/S2600WFT, BIOS SE5C620.86B.02.01.0008.031920191559 03/19/2019 [ 160.767642] Workqueue: eventsunbound bpfmapfreedeferred [ 160.773308] RIP: 0010:devmapfree+0x77/0x170 [ 160.777735] Code: 00 e8 fd 91 ed ff e8 b8 73 ed ff 41 83 7d 18 19 74 6e 41 8b 45 24 49 8b bd f8 00 00 00 31 db 85 c0 74 48 48 63 c3 48 8d 04 c7 <48> 8b 28 48 85 ed 74 30 48 8b 7d 18 48 85 ff 74 05 e8 b3 52 fa ff [ 160.796777] RSP: 0018:ffffc9000ee1fe38 EFLAGS: 00010202 [ 160.802086] RAX: ffffc8fc2c001000 RBX: 0000000080000000 RCX: 0000000000000024 [ 160.809331] RDX: 0000000000000000 RSI: 0000000000000024 RDI: ffffc9002c001000 [ 160.816576] RBP: 0000000000000000 R08: 0000000000000023 R09: 0000000000000001 [ 160.823823] R10: 0000000000000001 R11: 00000000000ee6b2 R12: dead000000000122 [ 160.831066] R13: ffff88810c928e00 R14: ffff8881002df405 R15: 0000000000000000 [ 160.838310] FS: 0000000000000000(0000) GS:ffff8897e0c40000(0000) knlGS:0000000000000000 [ 160.846528] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 160.852357] CR2: ffffc8fc2c001000 CR3: 0000000005c32006 CR4: 00000000007726f0 [ 160.859604] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 160.866847] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 160.874092] PKRU: 55555554 [ 160.876847] Call Trace: [ 160.879338] <TASK> [ 160.881477] ? die+0x20/0x60 [ 160.884586] ? pagefaultoops+0x15a/0x450 [ 160.888746] ? searchextable+0x22/0x30 [ 160.892647] ? searchbpfextables+0x5f/0x80 [ 160.896988] ? excpagefault+0xa9/0x140 [ 160.900973] ? asmexcpagefault+0x22/0x30 [ 160.905232] ? devmapfree+0x77/0x170 [ 160.909043] ? devmapfree+0x58/0x170 [ 160.912857] bpfmapfreedeferred+0x51/0x90 [ 160.917196] processonework+0x142/0x370 [ 160.921272] workerthread+0x29e/0x3b0 [ 160.925082] ? rescuerthread+0x4b0/0x4b0 [ 160.929157] kthread+0xd4/0x110 [ 160.932355] ? kthreadpark+0x80/0x80 [ 160.936079] retfromfork+0x2d/0x50 [ 160.943396] ? kthreadpark+0x80/0x80 [ 160.950803] retfromforkasm+0x11/0x20 [ 160.958482] </TASK>

— NVD

This CVE was automatically created from a reference found in an email or other text. If you are reading this, then this CVE entry is probably erroneous, since this text should be replaced by the official CVE description automatically.

— Launchpad