In the Linux kernel, the following vulnerability has been resolved:
LoongArch: BPF: Prevent out-of-bounds memory access
The test_tag test triggers an unhandled page fault:
[ 130.640218] CPU 0 Unable to handle kernel paging request at virtual address ffff80001b898004, era == 9000000003137f7c, ra == 9000000003139e70 [ 130.640501] Oops[#3]: [ 130.640553] CPU: 0 PID: 1326 Comm: test_tag Tainted: G D O 6.7.0-rc4-loong-devel-gb62ab1a397cf #47 61985c1d94084daa2432f771daa45b56b10d8d2a [ 130.640764] Hardware name: QEMU QEMU Virtual Machine, BIOS unknown 2/2/2022 [ 130.640874] pc 9000000003137f7c ra 9000000003139e70 tp 9000000104cb4000 sp 9000000104cb7a40 [ 130.641001] a0 ffff80001b894000 a1 ffff80001b897ff8 a2 000000006ba210be a3 0000000000000000 [ 130.641128] a4 000000006ba210be a5 00000000000000f1 a6 00000000000000b3 a7 0000000000000000 [ 130.641256] t0 0000000000000000 t1 00000000000007f6 t2 0000000000000000 t3 9000000004091b70 [ 130.641387] t4 000000006ba210be t5 0000000000000004 t6 fffffffffffffff0 t7 90000000040913e0 [ 130.641512] t8 0000000000000005 u0 0000000000000dc0 s9 0000000000000009 s0 9000000104cb7ae0 [ 130.641641] s1 00000000000007f6 s2 0000000000000009 s3 0000000000000095 s4 0000000000000000 [ 130.641771] s5 ffff80001b894000 s6 ffff80001b897fb0 s7 9000000004090c50 s8 0000000000000000 [ 130.641900] ra: 9000000003139e70 build_body+0x1fcc/0x4988 [ 130.642007] ERA: 9000000003137f7c build_body+0xd8/0x4988 [ 130.642112] CRMD: 000000b0 (PLV0 -IE -DA +PG DACF=CC DACM=CC -WE) [ 130.642261] PRMD: 00000004 (PPLV0 +PIE -PWE) [ 130.642353] EUEN: 00000003 (+FPE +SXE -ASXE -BTE) [ 130.642458] ECFG: 00071c1c (LIE=2-4,10-12 VS=7) [ 130.642554] ESTAT: 00010000 [PIL] (IS= ECode=1 EsubCode=0) [ 130.642658] BADV: ffff80001b898004 [ 130.642719] PRID: 0014c010 (Loongson-64bit, Loongson-3A5000) [ 130.642815] Modules linked in: [last unloaded: bpf_testmod(O)] [ 130.642924] Process test_tag (pid: 1326, threadinfo=00000000f7f4015f, task=000000006499f9fd) [ 130.643062] Stack : 0000000000000000 9000000003380724 0000000000000000 0000000104cb7be8 [ 130.643213] 0000000000000000 25af8d9b6e600558 9000000106250ea0 9000000104cb7ae0 [ 130.643378] 0000000000000000 0000000000000000 9000000104cb7be8 90000000049f6000 [ 130.643538] 0000000000000090 9000000106250ea0 ffff80001b894000 ffff80001b894000 [ 130.643685] 00007ffffb917790 900000000313ca94 0000000000000000 0000000000000000 [ 130.643831] ffff80001b894000 0000000000000ff7 0000000000000000 9000000100468000 [ 130.643983] 0000000000000000 0000000000000000 0000000000000040 25af8d9b6e600558 [ 130.644131] 0000000000000bb7 ffff80001b894048 0000000000000000 0000000000000000 [ 130.644276] 9000000104cb7be8 90000000049f6000 0000000000000090 9000000104cb7bdc [ 130.644423] ffff80001b894000 0000000000000000 00007ffffb917790 90000000032acfb0 [ 130.644572] … [ 130.644629] Call Trace: [ 130.644641] [<9000000003137f7c>] build_body+0xd8/0x4988 [ 130.644785] [<900000000313ca94>] bpf_int_jit_compile+0x228/0x4ec [ 130.644891] [<90000000032acfb0>] bpf_prog_select_runtime+0x158/0x1b0 [ 130.645003] [<90000000032b3504>] bpf_prog_load+0x760/0xb44 [ 130.645089] [<90000000032b6744>] __sys_bpf+0xbb8/0x2588 [ 130.645175] [<90000000032b8388>] sys_bpf+0x20/0x2c [ 130.645259] [<9000000003f6ab38>] do_syscall+0x7c/0x94 [ 130.645369] [<9000000003121c5c>] handle_syscall+0xbc/0x158 [ 130.645507] [ 130.645539] Code: 380839f6 380831f9 28412bae <24000ca6> 004081ad 0014cb50 004083e8 02bff34c 58008e91 [ 130.645729] [ 130.646418] —[ end trace 0000000000000000 ]—
On my machine, which has CONFIG_PAGE_SIZE_16KB=y, the test failed at loading a BPF prog with 2039 instructions:
prog = (struct bpf_prog *)ffff80001b894000 insn = (struct bpf_insn *)(prog->insnsi)fff —truncated—
The product performs operations on a memory buffer, but it can read from or write to a memory location that is outside of the intended boundary of the buffer.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Linux_kernel | Linux | * | 6.1.75 (excluding) |
| Linux_kernel | Linux | 6.2.0 (including) | 6.6.14 (excluding) |
| Linux_kernel | Linux | 6.7.0 (including) | 6.7.2 (excluding) |
Certain languages allow direct addressing of memory locations and do not automatically ensure that these locations are valid for the memory buffer that is being referenced. This can cause read or write operations to be performed on memory locations that may be associated with other variables, data structures, or internal program data. As a result, an attacker may be able to execute arbitrary code, alter the intended control flow, read sensitive information, or cause the system to crash.
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
For example, many languages that perform their own memory management, such as Java and Perl, are not subject to buffer overflows. Other languages, such as Ada and C#, typically provide overflow protection, but the protection can be disabled by the programmer.
Be wary that a language’s interface to native code may still be subject to overflows, even if the language itself is theoretically safe.
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Examples include the Safe C String Library (SafeStr) by Messier and Viega [REF-57], and the Strsafe.h library from Microsoft [REF-56]. These libraries provide safer versions of overflow-prone string-handling functions.
Use automatic buffer overflow detection mechanisms that are offered by certain compilers or compiler extensions. Examples include: the Microsoft Visual Studio /GS flag, Fedora/Red Hat FORTIFY_SOURCE GCC flag, StackGuard, and ProPolice, which provide various mechanisms including canary-based detection and range/index checking.
D3-SFCV (Stack Frame Canary Validation) from D3FEND [REF-1334] discusses canary-based detection in detail.
Consider adhering to the following rules when allocating and managing an application’s memory:
Run or compile the software using features or extensions that randomly arrange the positions of a program’s executable and libraries in memory. Because this makes the addresses unpredictable, it can prevent an attacker from reliably jumping to exploitable code.
Examples include Address Space Layout Randomization (ASLR) [REF-58] [REF-60] and Position-Independent Executables (PIE) [REF-64]. Imported modules may be similarly realigned if their default memory addresses conflict with other modules, in a process known as “rebasing” (for Windows) and “prelinking” (for Linux) [REF-1332] using randomly generated addresses. ASLR for libraries cannot be used in conjunction with prelink since it would require relocating the libraries at run-time, defeating the whole purpose of prelinking.
For more information on these techniques see D3-SAOR (Segment Address Offset Randomization) from D3FEND [REF-1335].
Use a CPU and operating system that offers Data Execution Protection (using hardware NX or XD bits) or the equivalent techniques that simulate this feature in software, such as PaX [REF-60] [REF-61]. These techniques ensure that any instruction executed is exclusively at a memory address that is part of the code segment.
For more information on these techniques see D3-PSEP (Process Segment Execution Prevention) from D3FEND [REF-1336].