CVE-2026-93167

Summary

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

csky: Fix a4/a5 restoration in syscall trace path

The syscall trace path reloads syscall arguments from pt_regs before calling the syscall handler. On C-SKY ABIv2, the 5th and 6th syscall arguments are prepared as stack arguments before invoking syscallid.

The current code adjusts sp before loading LSAVE_A4 and LSAVE_A5. Since those offsets are relative to the original pt_regs base, loading them after changing sp fetches the wrong slots. As a result, traced syscalls that use the 5th or 6th argument may receive corrupted arguments.

This is visible with mmap2(), which takes six arguments. A small PTRACE_SYSCALL reproducer opens a file and maps one page with:

mmap(NULL, 4096, PROT_READ | PROT_EXEC, MAP_PRIVATE, fd, 0)

Before the fix, the traced child fails the mmap and exits with 12. After the fix, the mapping succeeds and the child exits with 0.

Fix the trace path by loading a4/a5 from pt_regs before changing sp.

Tested on: ck860f, linux-4.19.15, C-SKY abiv2

Affected Software

VendorProductVersion RangeStatus
LinuxLinuxe0bbb53843b5fdfe464b099217e3b9d97e8a75d7 < e9ae8e86eed68bea5d2670eadf61938a43bd2263affected
LinuxLinuxe0bbb53843b5fdfe464b099217e3b9d97e8a75d7 < 64e3ec7a71d3b715e2567f19f64207f04999bb0caffected
LinuxLinuxe0bbb53843b5fdfe464b099217e3b9d97e8a75d7 < 863fa63fd1491f201ac819f805a8db98d2a32c3daffected
LinuxLinuxe0bbb53843b5fdfe464b099217e3b9d97e8a75d7 < e71a3dc5b8d2ea4d9cfbdb135d6b7777de84212eaffected
LinuxLinuxe0bbb53843b5fdfe464b099217e3b9d97e8a75d7 < 31c81b376e5f058c7f2c94f69719cf7caec2fc3faffected
LinuxLinuxe0bbb53843b5fdfe464b099217e3b9d97e8a75d7 < a776afa89424570bfa637ebf812ca281a5732904affected
LinuxLinuxe0bbb53843b5fdfe464b099217e3b9d97e8a75d7 < 343aa5275484d627c921a42e8e115cae366be5deaffected
LinuxLinuxe0bbb53843b5fdfe464b099217e3b9d97e8a75d7 < abb81e5ce7d995baa41556b8125fa59e28ba3be8affected
LinuxLinux108681048cf728a8570e036c34ebd7daa43133b4affected
LinuxLinux3a5837c692918c229baf63fe7950965d27c48ac2affected
LinuxLinux5.4.47 < 5.5affected
LinuxLinux5.6.19 < 5.7affected
LinuxLinux5.7affected
LinuxLinux0 < 5.7unaffected
LinuxLinux5.10.270 <= 5.10.*unaffected
LinuxLinux5.15.221 <= 5.15.*unaffected
LinuxLinux6.1.188 <= 6.1.*unaffected
LinuxLinux6.6.157 <= 6.6.*unaffected
LinuxLinux6.12.110 <= 6.12.*unaffected
LinuxLinux6.18.52 <= 6.18.*unaffected
LinuxLinux7.2.6 <= 7.2.*unaffected
LinuxLinux7.3-rc1 <= *unaffected

Weaknesses

References