Check that size would not overflow before calculation (and return -EOVERFLOW if it will), to prevent potential out-of-bounds write with the following copy_from_user. Add the same check to kprobe_multi_resolve_syms in case it will be called from elsewhere in the future. The INT_MAX checks are performed in order to avoid triggering kvmalloc_node warning [1].
[1] https://lore.kernel.org/lkml/cfe6abea-8d00-8f8c-f84c-e6f27753b5d1@fb.com/
Fixes: 0dcac272540613d4 ("bpf: Add multi kprobe link") Signed-off-by: Eugene Syromiatnikov esyr@redhat.com --- kernel/trace/bpf_trace.c | 13 ++++++++----- 1 file changed, 8 insertions(+), 5 deletions(-)
diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index d8553f4..26cf99c 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2352,13 +2352,15 @@ static int kprobe_multi_resolve_syms(const void __user *usyms, u32 cnt, unsigned long *addrs) { - unsigned long addr, size; + unsigned long addr, sym_size; + u32 size; const char __user **syms; int err = -ENOMEM; unsigned int i; char *func;
- size = cnt * sizeof(*syms); + if (check_mul_overflow(cnt, (u32)sizeof(*syms), &size) || size > INT_MAX) + return -EOVERFLOW; syms = kvzalloc(size, GFP_KERNEL); if (!syms) return -ENOMEM; @@ -2382,9 +2384,9 @@ 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; @@ -2429,7 +2431,8 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr if (!cnt) return -EINVAL;
- size = cnt * sizeof(*addrs); + if (check_mul_overflow(cnt, (u32)sizeof(*addrs), &size) || size > INT_MAX) + return -EOVERFLOW; addrs = kvmalloc(size, GFP_KERNEL); if (!addrs) return -ENOMEM;