exploit: ptrace POKETEXT code patching#29
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nataliakokoromyti wants to merge 3 commits intogpu-mode:masterfrom
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exploit: ptrace POKETEXT code patching#29nataliakokoromyti wants to merge 3 commits intogpu-mode:masterfrom
nataliakokoromyti wants to merge 3 commits intogpu-mode:masterfrom
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Fork child process that uses ptrace(PTRACE_ATTACH) + PTRACE_POKETEXT to patch cudaEventElapsedTime .text code. PTRACE_POKETEXT uses FOLL_FORCE internally, bypassing read-only page protections. Bypasses PR_SET_DUMPABLE=0 by re-enabling dumpable via prctl (no seccomp filter prevents this). Uses PR_SET_PTRACER for Yama LSM. Defense: block ptrace() syscall (SYS_ptrace=101).
Updated docstring to clarify ptrace exploit details and defenses.
nataliakokoromyti
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The benchmark harness sets PR_SET_DUMPABLE=0 to block ptrace, but has no seccomp filters, so you just call prctl(PR_SET_DUMPABLE, 1) to undo it. Then fork a child, PTRACE_ATTACH the parent, PTRACE_POKETEXT 9 bytes of shellcode over cudaEventElapsedTime. POKETEXT uses FOLL_FORCE internally so it writes straight through read-only .text pages. Reports 1.0us (or any other float of our choice since shellcode is just mov dword [rdi], <ieee754_bits>; xor eax,eax; ret so we can change the 4 bytes and get whatever timing we want).
Mechanism
prctl(PR_SET_DUMPABLE, 1)— re-enable ptrace attach (harness disables this but has no seccomp)prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY)— bypass Yama LSMPTRACE_ATTACH→PTRACE_POKETEXT(writes 9-byte shellcode)mov dword [rdi], 0x3A83126F; xor eax,eax; ret— sets*ms = 0.001f, returnscudaSuccessResults