| From bippy-5f407fcff5a0 Mon Sep 17 00:00:00 2001 |
| From: Greg Kroah-Hartman <gregkh@linuxfoundation.org> |
| To: <linux-cve-announce@vger.kernel.org> |
| Reply-to: <cve@kernel.org>, <linux-kernel@vger.kernel.org> |
| Subject: CVE-2022-48998: powerpc/bpf/32: Fix Oops on tail call tests |
| |
| Description |
| =========== |
| |
| In the Linux kernel, the following vulnerability has been resolved: |
| |
| powerpc/bpf/32: Fix Oops on tail call tests |
| |
| test_bpf tail call tests end up as: |
| |
| test_bpf: #0 Tail call leaf jited:1 85 PASS |
| test_bpf: #1 Tail call 2 jited:1 111 PASS |
| test_bpf: #2 Tail call 3 jited:1 145 PASS |
| test_bpf: #3 Tail call 4 jited:1 170 PASS |
| test_bpf: #4 Tail call load/store leaf jited:1 190 PASS |
| test_bpf: #5 Tail call load/store jited:1 |
| BUG: Unable to handle kernel data access on write at 0xf1b4e000 |
| Faulting instruction address: 0xbe86b710 |
| Oops: Kernel access of bad area, sig: 11 [#1] |
| BE PAGE_SIZE=4K MMU=Hash PowerMac |
| Modules linked in: test_bpf(+) |
| CPU: 0 PID: 97 Comm: insmod Not tainted 6.1.0-rc4+ #195 |
| Hardware name: PowerMac3,1 750CL 0x87210 PowerMac |
| NIP: be86b710 LR: be857e88 CTR: be86b704 |
| REGS: f1b4df20 TRAP: 0300 Not tainted (6.1.0-rc4+) |
| MSR: 00009032 <EE,ME,IR,DR,RI> CR: 28008242 XER: 00000000 |
| DAR: f1b4e000 DSISR: 42000000 |
| GPR00: 00000001 f1b4dfe0 c11d2280 00000000 00000000 00000000 00000002 00000000 |
| GPR08: f1b4e000 be86b704 f1b4e000 00000000 00000000 100d816a f2440000 fe73baa8 |
| GPR16: f2458000 00000000 c1941ae4 f1fe2248 00000045 c0de0000 f2458030 00000000 |
| GPR24: 000003e8 0000000f f2458000 f1b4dc90 3e584b46 00000000 f24466a0 c1941a00 |
| NIP [be86b710] 0xbe86b710 |
| LR [be857e88] __run_one+0xec/0x264 [test_bpf] |
| Call Trace: |
| [f1b4dfe0] [00000002] 0x2 (unreliable) |
| Instruction dump: |
| XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX |
| XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX XXXXXXXX |
| ---[ end trace 0000000000000000 ]--- |
| |
| This is a tentative to write above the stack. The problem is encoutered |
| with tests added by commit 38608ee7b690 ("bpf, tests: Add load store |
| test case for tail call") |
| |
| This happens because tail call is done to a BPF prog with a different |
| stack_depth. At the time being, the stack is kept as is when the caller |
| tail calls its callee. But at exit, the callee restores the stack based |
| on its own properties. Therefore here, at each run, r1 is erroneously |
| increased by 32 - 16 = 16 bytes. |
| |
| This was done that way in order to pass the tail call count from caller |
| to callee through the stack. As powerpc32 doesn't have a red zone in |
| the stack, it was necessary the maintain the stack as is for the tail |
| call. But it was not anticipated that the BPF frame size could be |
| different. |
| |
| Let's take a new approach. Use register r4 to carry the tail call count |
| during the tail call, and save it into the stack at function entry if |
| required. This means the input parameter must be in r3, which is more |
| correct as it is a 32 bits parameter, then tail call better match with |
| normal BPF function entry, the down side being that we move that input |
| parameter back and forth between r3 and r4. That can be optimised later. |
| |
| Doing that also has the advantage of maximising the common parts between |
| tail calls and a normal function exit. |
| |
| With the fix, tail call tests are now successfull: |
| |
| test_bpf: #0 Tail call leaf jited:1 53 PASS |
| test_bpf: #1 Tail call 2 jited:1 115 PASS |
| test_bpf: #2 Tail call 3 jited:1 154 PASS |
| test_bpf: #3 Tail call 4 jited:1 165 PASS |
| test_bpf: #4 Tail call load/store leaf jited:1 101 PASS |
| test_bpf: #5 Tail call load/store jited:1 141 PASS |
| test_bpf: #6 Tail call error path, max count reached jited:1 994 PASS |
| test_bpf: #7 Tail call count preserved across function calls jited:1 140975 PASS |
| test_bpf: #8 Tail call error path, NULL target jited:1 110 PASS |
| test_bpf: #9 Tail call error path, index out of range jited:1 69 PASS |
| test_bpf: test_tail_calls: Summary: 10 PASSED, 0 FAILED, [10/10 JIT'ed] |
| |
| The Linux kernel CVE team has assigned CVE-2022-48998 to this issue. |
| |
| |
| Affected and fixed versions |
| =========================== |
| |
| Issue introduced in 5.13 with commit 51c66ad849a703d9bbfd7704c941827aed0fd9fd and fixed in 6.0.12 with commit 747a6e547240baaaf41874d27333b87b87cfd24c |
| Issue introduced in 5.13 with commit 51c66ad849a703d9bbfd7704c941827aed0fd9fd and fixed in 6.1 with commit 89d21e259a94f7d5582ec675aa445f5a79f347e4 |
| |
| Please see https://www.kernel.org for a full list of currently supported |
| kernel versions by the kernel community. |
| |
| Unaffected versions might change over time as fixes are backported to |
| older supported kernel versions. The official CVE entry at |
| https://cve.org/CVERecord/?id=CVE-2022-48998 |
| will be updated if fixes are backported, please check that for the most |
| up to date information about this issue. |
| |
| |
| Affected files |
| ============== |
| |
| The file(s) affected by this issue are: |
| arch/powerpc/net/bpf_jit_comp32.c |
| |
| |
| Mitigation |
| ========== |
| |
| The Linux kernel CVE team recommends that you update to the latest |
| stable kernel version for this, and many other bugfixes. Individual |
| changes are never tested alone, but rather are part of a larger kernel |
| release. Cherry-picking individual commits is not recommended or |
| supported by the Linux kernel community at all. If however, updating to |
| the latest release is impossible, the individual changes to resolve this |
| issue can be found at these commits: |
| https://git.kernel.org/stable/c/747a6e547240baaaf41874d27333b87b87cfd24c |
| https://git.kernel.org/stable/c/89d21e259a94f7d5582ec675aa445f5a79f347e4 |
