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Yama: handle 32-bit userspace prctl

When running a 64-bit kernel and receiving prctls from a 32-bit
userspace, the "-1" used as an unsigned long will end up being
misdetected. The kernel is looking for 0xffffffffffffffff instead of
0xffffffff. Since prctl lacks a distinct compat interface, Yama needs
to handle this translation itself. As such, support either value as
meaning PR_SET_PTRACER_ANY, to avoid breaking the ABI for 64-bit.

Signed-off-by: Kees Cook <>
Acked-by: John Johansen <>
Signed-off-by: James Morris <>
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commit 2e4930eb7c8fb20a39dfb5f8a8f80402710dcea8 1 parent c6993e4
@kees kees authored James Morris committed
Showing with 1 addition and 1 deletion.
  1. +1 −1  security/yama/yama_lsm.c
2  security/yama/yama_lsm.c
@@ -143,7 +143,7 @@ int yama_task_prctl(int option, unsigned long arg2, unsigned long arg3,
if (arg2 == 0) {
yama_ptracer_del(NULL, myself);
rc = 0;
- } else if (arg2 == PR_SET_PTRACER_ANY) {
+ } else if (arg2 == PR_SET_PTRACER_ANY || (int)arg2 == -1) {
rc = yama_ptracer_add(NULL, myself);
} else {
struct task_struct *tracer;
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