CVE-2024-26589: bpf: Reject variable offset alu on PTR_TO_FLOW_KEYS
First published: Thu Feb 22 2024(Updated: )
bpf: Reject variable offset alu on PTR_TO_FLOW_KEYS For PTR_TO_FLOW_KEYS, check_flow_keys_access() only uses fixed off for validation. However, variable offset ptr alu is not prohibited for this ptr kind. So the variable offset is not checked. The following prog is accepted: func#0 @0 0: R1=ctx() R10=fp0 0: (bf) r6 = r1 ; R1=ctx() R6_w=ctx() 1: (79) r7 = *(u64 *)(r6 +144) ; R6_w=ctx() R7_w=flow_keys() 2: (b7) r8 = 1024 ; R8_w=1024 3: (37) r8 /= 1 ; R8_w=scalar() 4: (57) r8 &= 1024 ; R8_w=scalar(smin=smin32=0, smax=umax=smax32=umax32=1024,var_off=(0x0; 0x400)) 5: (0f) r7 += r8 mark_precise: frame0: last_idx 5 first_idx 0 subseq_idx -1 mark_precise: frame0: regs=r8 stack= before 4: (57) r8 &= 1024 mark_precise: frame0: regs=r8 stack= before 3: (37) r8 /= 1 mark_precise: frame0: regs=r8 stack= before 2: (b7) r8 = 1024 6: R7_w=flow_keys(smin=smin32=0,smax=umax=smax32=umax32=1024,var_off =(0x0; 0x400)) R8_w=scalar(smin=smin32=0,smax=umax=smax32=umax32=1024, var_off=(0x0; 0x400)) 6: (79) r0 = *(u64 *)(r7 +0) ; R0_w=scalar() 7: (95) exit This prog loads flow_keys to r7, and adds the variable offset r8 to r7, and finally causes out-of-bounds access: BUG: unable to handle page fault for address: ffffc90014c80038 [...] Call Trace: <TASK> bpf_dispatcher_nop_func include/linux/bpf.h:1231 [inline] __bpf_prog_run include/linux/filter.h:651 [inline] bpf_prog_run include/linux/filter.h:658 [inline] bpf_prog_run_pin_on_cpu include/linux/filter.h:675 [inline] bpf_flow_dissect+0x15f/0x350 net/core/flow_dissector.c:991 bpf_prog_test_run_flow_dissector+0x39d/0x620 net/bpf/test_run.c:1359 bpf_prog_test_run kernel/bpf/syscall.c:4107 [inline] __sys_bpf+0xf8f/0x4560 kernel/bpf/syscall.c:5475 __do_sys_bpf kernel/bpf/syscall.c:5561 [inline] __se_sys_bpf kernel/bpf/syscall.c:5559 [inline] __x64_sys_bpf+0x73/0xb0 kernel/bpf/syscall.c:5559 do_syscall_x64 arch/x86/entry/common.c:52 [inline] do_syscall_64+0x3f/0x110 arch/x86/entry/common.c:83 entry_SYSCALL_64_after_hwframe+0x63/0x6b Fix this by rejecting ptr alu with variable offset on flow_keys. Applying the patch rejects the program with "R7 pointer arithmetic on flow_keys prohibited".
Credit: 416baaa9-dc9f-4396-8d5f-8c081fb06d67 416baaa9-dc9f-4396-8d5f-8c081fb06d67
| Affected Software | Affected Version | How to fix |
|---|---|---|
| Linux Linux kernel | >=4.20<5.15.148 | |
| Linux Linux kernel | >=5.16.0<6.1.75 | |
| Linux Linux kernel | >=6.2.0<6.6.14 | |
| Linux Linux kernel | >=6.7.0<6.7.2 | |
| debian/linux | <=5.10.223-1<=5.10.226-1 | 6.1.123-1 6.1.119-1 6.12.6-1 6.12.9-1 |
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Reference Links
- https://git.kernel.org/stable/c/1b500d5d6cecf98dd6ca88bc9e7ae1783c83e6d3
- https://git.kernel.org/stable/c/22c7fa171a02d310e3a3f6ed46a698ca8a0060ed
- https://git.kernel.org/stable/c/29ffa63f21bcdcef3e36b03cccf9d0cd031f6ab0
- https://git.kernel.org/stable/c/4108b86e324da42f7ed425bd71632fd844300dc8
- https://git.kernel.org/stable/c/e8d3872b617c21100c5ee4f64e513997a68c2e3d
- https://launchpad.net/bugs/cve/CVE-2024-26589
- https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-26589
- https://nvd.nist.gov/vuln/detail/CVE-2024-26589
- https://security-tracker.debian.org/tracker/CVE-2024-26589
- https://ubuntu.com/security/CVE-2024-26589
- https://git.kernel.org/linus/22c7fa171a02d310e3a3f6ed46a698ca8a0060ed
- https://bugzilla.redhat.com/show_bug.cgi/show_bug.cgi?id=2265666
- https://access.redhat.com/security/cve/CVE-2024-26589
- https://access.redhat.com/errata/RHSA-2024:9315
- https://bugzilla.redhat.com/show_bug.cgi?id=2265657
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