Description

In the Linux kernel, the following vulnerability has been resolved: arm64: probes: Fix uprobes for big-endian kernels The arm64 uprobes code is broken for big-endian kernels as it doesn't convert the in-memory instruction encoding (which is always little-endian) into the kernel's native endianness before analyzing and simulating instructions. This may result in a few distinct problems: * The kernel may may erroneously reject probing an instruction which can safely be probed. * The kernel may erroneously erroneously permit stepping an instruction out-of-line when that instruction cannot be stepped out-of-line safely. * The kernel may erroneously simulate instruction incorrectly dur to interpretting the byte-swapped encoding. The endianness mismatch isn't caught by the compiler or sparse because: * The arch_uprobe::{insn,ixol} fields are encoded as arrays of u8, so the compiler and sparse have no idea these contain a little-endian 32-bit value. The core uprobes code populates these with a memcpy() which similarly does not handle endianness. * While the uprobe_opcode_t type is an alias for __le32, both arch_uprobe_analyze_insn() and arch_uprobe_skip_sstep() cast from u8[] to the similarly-named probe_opcode_t, which is an alias for u32. Hence there is no endianness conversion warning. Fix this by changing the arch_uprobe::{insn,ixol} fields to __le32 and adding the appropriate __le32_to_cpu() conversions prior to consuming the instruction encoding. The core uprobes copies these fields as opaque ranges of bytes, and so is unaffected by this change. At the same time, remove MAX_UINSN_BYTES and consistently use AARCH64_INSN_SIZE for clarity. Tested with the following: | #include <stdio.h> | #include <stdbool.h> | | #define noinline __attribute__((noinline)) | | static noinline void *adrp_self(void) | { | void *addr; | | asm volatile( | " adrp %x0, adrp_self\n" | " add %x0, %x0, :lo12:adrp_self\n" | : "=r" (addr)); | } | | | int main(int argc, char *argv) | { | void *ptr = adrp_self(); | bool equal = (ptr == adrp_self); | | printf("adrp_self => %p\n" | "adrp_self() => %p\n" | "%s\n", | adrp_self, ptr, equal ? "EQUAL" : "NOT EQUAL"); | | return 0; | } .... where the adrp_self() function was compiled to: | 00000000004007e0 <adrp_self>: | 4007e0: 90000000 adrp x0, 400000 <__ehdr_start> | 4007e4: 911f8000 add x0, x0, #0x7e0 | 4007e8: d65f03c0 ret Before this patch, the ADRP is not recognized, and is assumed to be steppable, resulting in corruption of the result: | # ./adrp-self | adrp_self => 0x4007e0 | adrp_self() => 0x4007e0 | EQUAL | # echo 'p /root/adrp-self:0x007e0' > /sys/kernel/tracing/uprobe_events | # echo 1 > /sys/kernel/tracing/events/uprobes/enable | # ./adrp-self | adrp_self => 0x4007e0 | adrp_self() => 0xffffffffff7e0 | NOT EQUAL After this patch, the ADRP is correctly recognized and simulated: | # ./adrp-self | adrp_self => 0x4007e0 | adrp_self() => 0x4007e0 | EQUAL | # | # echo 'p /root/adrp-self:0x007e0' > /sys/kernel/tracing/uprobe_events | # echo 1 > /sys/kernel/tracing/events/uprobes/enable | # ./adrp-self | adrp_self => 0x4007e0 | adrp_self() => 0x4007e0 | EQUAL

Affected Products 10

References 10

• git.kernel.org https://git.kernel.org/stable/c/13f8f1e05f1dc36dbba6cba0ae03354c0dafcde7
  Patch
• git.kernel.org https://git.kernel.org/stable/c/14841bb7a531b96e2dde37423a3b33e75147c60d
  Patch
• git.kernel.org https://git.kernel.org/stable/c/3d2530c65be04e93720e30f191a7cf1a3aa8b51c
  Patch
• git.kernel.org https://git.kernel.org/stable/c/8165bf83b8a64be801d59cd2532b0d1ffed74d00
  Patch
• git.kernel.org https://git.kernel.org/stable/c/b6a638cb600e13f94b5464724eaa6ab7f3349ca2
  Patch
• git.kernel.org https://git.kernel.org/stable/c/cf60d19d40184e43d9a624e55a0da73be09e938d
  Patch
• git.kernel.org https://git.kernel.org/stable/c/cf9ddf9ed94c15564a05bbf6e9f18dffa0c7df80
  Patch
• git.kernel.org https://git.kernel.org/stable/c/e6ab336213918575124d6db43dc5d3554526242e
  Patch
• lists.debian.org https://lists.debian.org/debian-lts-announce/2025/01/msg00001.html
• lists.debian.org https://lists.debian.org/debian-lts-announce/2025/03/msg00002.html

Remediation

• git.kernel.org https://git.kernel.org/stable/c/13f8f1e05f1dc36dbba6cba0ae03354c0dafcde7
  Patch
• git.kernel.org https://git.kernel.org/stable/c/14841bb7a531b96e2dde37423a3b33e75147c60d
  Patch
• git.kernel.org https://git.kernel.org/stable/c/3d2530c65be04e93720e30f191a7cf1a3aa8b51c
  Patch
• git.kernel.org https://git.kernel.org/stable/c/8165bf83b8a64be801d59cd2532b0d1ffed74d00
  Patch
• git.kernel.org https://git.kernel.org/stable/c/b6a638cb600e13f94b5464724eaa6ab7f3349ca2
  Patch
• git.kernel.org https://git.kernel.org/stable/c/cf60d19d40184e43d9a624e55a0da73be09e938d
  Patch
• git.kernel.org https://git.kernel.org/stable/c/cf9ddf9ed94c15564a05bbf6e9f18dffa0c7df80
  Patch
• git.kernel.org https://git.kernel.org/stable/c/e6ab336213918575124d6db43dc5d3554526242e
  Patch