For compat processes, userspace pointer size is different. Since the copied array is iterated anyway, the simplest fix seems to be copy the user-supplied array as-is and the iterate as an array of native or compat pointers, depending on the in_compat_syscall() value.
Fixes: 0dcac272540613d4 ("bpf: Add multi kprobe link") Signed-off-by: Eugene Syromiatnikov esyr@redhat.com --- kernel/trace/bpf_trace.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index d228440..5b0cf54 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2352,16 +2352,21 @@ static int kprobe_multi_resolve_syms(const void __user *usyms, u32 cnt, unsigned long *addrs) { - unsigned long addr, size; + unsigned long addr; + size_t sym_size; + u32 size, elem_size; const char __user **syms; + compat_uptr_t __user *compat_syms; int err = -ENOMEM; unsigned int i; char *func;
- if (check_mul_overflow(cnt, sizeof(*syms), &size)) + elem_size = in_compat_syscall() ? sizeof(*compat_syms) : sizeof(*syms); + if (check_mul_overflow(cnt, elem_size, &size)) return -EOVERFLOW; - size = cnt * sizeof(*syms); + size = cnt * elem_size; syms = kvzalloc(size, GFP_KERNEL); + compat_syms = (void *)syms; if (!syms) return -ENOMEM;
@@ -2375,7 +2380,10 @@ kprobe_multi_resolve_syms(const void __user *usyms, u32 cnt, }
for (i = 0; i < cnt; i++) { - err = strncpy_from_user(func, syms[i], KSYM_NAME_LEN); + const char __user *ufunc = in_compat_syscall() + ? (char __user *)(uintptr_t)compat_syms[i] + : syms[i]; + err = strncpy_from_user(func, ufunc, KSYM_NAME_LEN); if (err == KSYM_NAME_LEN) err = -E2BIG; if (err < 0) @@ -2384,9 +2392,9 @@ kprobe_multi_resolve_syms(const void __user *usyms, u32 cnt, addr = kallsyms_lookup_name(func); if (!addr) goto error; - if (!kallsyms_lookup_size_offset(addr, &size, NULL)) + if (!kallsyms_lookup_size_offset(addr, &sym_size, NULL)) goto error; - addr = ftrace_location_range(addr, addr + size - 1); + addr = ftrace_location_range(addr, addr + sym_size - 1); if (!addr) goto error; addrs[i] = addr;