[bpf,v4,1/3] bpf_trace: check size for overflow in bpf_kprobe_multi_link_attach

Commit Message

Eugene Syromiatnikov May 19, 2022, 6:14 p.m. UTC

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/[e-mail]/

Fixes: 0dcac272540613d4 ("bpf: Add multi kprobe link")
Signed-off-by: Eugene Syromiatnikov <[e-mail]>
---
 kernel/trace/bpf_trace.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

Comments

Yonghong Song May 19, 2022, 7:22 p.m. UTC | #1

On 5/19/22 11:14 AM, Eugene Syromiatnikov wrote:
> 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/[e-mail]/
> 
> Fixes: 0dcac272540613d4 ("bpf: Add multi kprobe link")
> Signed-off-by: Eugene Syromiatnikov <[e-mail]>

Acked-by: Yonghong Song <[e-mail]>

Patch

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;