Bugfix: 32-bit compat program false positive

32-bit programs on x86-64 may use a fast syscall method, whose code resides in the VDSO VMA. This VMA is not file backed, so it was incorrectly detected as anonymous memory.
aquasecurity · Oct 7, 2024 · 9376b56 · 9376b56
1 parent 3055433
commit 9376b56
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Showing 8 changed files with 38 additions and 8 deletions.
diff --git a/go.mod b/go.mod
@@ -8,6 +8,7 @@ require (
 	github.com/IBM/fluent-forward-go v0.2.2
 	github.com/Masterminds/sprig/v3 v3.2.3
 	github.com/aquasecurity/libbpfgo v0.7.0-libbpf-1.4.0.20240729111821-61d531acf4ca
+	github.com/aquasecurity/libbpfgo/helpers v0.4.5
 	github.com/aquasecurity/tracee/api v0.0.0-20240905132323-d1eaeef6a19f
 	github.com/aquasecurity/tracee/signatures/helpers v0.0.0-20240607205742-90c301111aee
 	github.com/aquasecurity/tracee/types v0.0.0-20240607205742-90c301111aee

diff --git a/go.sum b/go.sum
@@ -406,6 +406,8 @@ github.com/agnivade/levenshtein v1.1.1/go.mod h1:veldBMzWxcCG2ZvUTKD2kJNRdCk5hVb
 github.com/antihax/optional v1.0.0/go.mod h1:uupD/76wgC+ih3iEmQUL+0Ugr19nfwCT1kdvxnR2qWY=
 github.com/aquasecurity/libbpfgo v0.7.0-libbpf-1.4.0.20240729111821-61d531acf4ca h1:OPbvwFFvR11c1bgOLhBq1R5Uk3hwUjHW2KfrdyJan9Y=
 github.com/aquasecurity/libbpfgo v0.7.0-libbpf-1.4.0.20240729111821-61d531acf4ca/go.mod h1:UpO6kTehEgAGGKR2twztBxvzjTiLiV/cb2xmlYb+TfE=
+github.com/aquasecurity/libbpfgo/helpers v0.4.5 h1:eCoLclL3yqv4N9jqGL3T/ckrLPms2r13C4V2xtU75yc=
+github.com/aquasecurity/libbpfgo/helpers v0.4.5/go.mod h1:j/TQLmsZpOIdF3CnJODzYngG4yu1YoDCoRMELxkQSSA=
 github.com/aquasecurity/tracee/api v0.0.0-20240905132323-d1eaeef6a19f h1:O4UmMQViaaP1wKL1eXe7C6VylwrUmUB5mYM+roqnUZg=
 github.com/aquasecurity/tracee/api v0.0.0-20240905132323-d1eaeef6a19f/go.mod h1:Gn6xVkaBkVe1pOQ0++uuHl+lMMClv0TPY8mCQ6j88aA=
 github.com/aquasecurity/tracee/signatures/helpers v0.0.0-20240607205742-90c301111aee h1:1KJy6Z2bSpmKQVPShU7hhbXgGVOgMwvzf9rjoWMTYEg=

diff --git a/pkg/ebpf/c/common/common.h b/pkg/ebpf/c/common/common.h
@@ -62,7 +62,7 @@ static __inline int has_prefix(char *prefix, char *str, int n)
     }
 
     // prefix is too long
-    return 0;
+    return 1;
 }
 
 #endif

diff --git a/pkg/ebpf/c/common/memory.h b/pkg/ebpf/c/common/memory.h
@@ -18,6 +18,8 @@ statfunc unsigned long get_vma_start(struct vm_area_struct *);
 statfunc struct vm_area_struct *find_vma(struct task_struct *task, u64 addr);
 statfunc bool vma_is_stack(struct vm_area_struct *vma);
 statfunc bool vma_is_heap(struct vm_area_struct *vma);
+statfunc bool vma_is_anon(struct vm_area_struct *vma);
+statfunc bool vma_is_vdso(struct vm_area_struct *vma);
 
 // FUNCTIONS
 
@@ -156,4 +158,17 @@ statfunc bool vma_is_anon(struct vm_area_struct *vma)
     return BPF_CORE_READ(vma, vm_file) == NULL;
 }
 
+statfunc bool vma_is_vdso(struct vm_area_struct *vma)
+{
+    struct vm_special_mapping *special_mapping =
+        (struct vm_special_mapping *) BPF_CORE_READ(vma, vm_private_data);
+    if (special_mapping == NULL)
+        return false;
+
+    // read only 6 characters (7 with NULL terminator), enough to compare with "[vdso]"
+    char mapping_name[7];
+    bpf_probe_read_str(&mapping_name, 7, BPF_CORE_READ(special_mapping, name));
+    return has_prefix("[vdso]", mapping_name, 6);
+}
+
 #endif
diff --git a/pkg/ebpf/c/tracee.bpf.c b/pkg/ebpf/c/tracee.bpf.c
@@ -5182,8 +5182,9 @@ statfunc enum vma_type get_vma_type(struct vm_area_struct *vma)
     if (vma_is_heap(vma))
         return VMA_HEAP;
 
-    if (vma_is_anon(vma))
+    if (vma_is_anon(vma) && !vma_is_vdso(vma)) {
         return VMA_ANON;
+    }
 
     return VMA_OTHER;
 }

diff --git a/pkg/ebpf/c/vmlinux.h b/pkg/ebpf/c/vmlinux.h
@@ -291,6 +291,16 @@ struct rb_node {
     struct rb_node *rb_left;
 } __attribute__((aligned(sizeof(long))));
 
+struct vm_area_struct;
+
+struct vm_operations_struct {
+    const char *(*name)(struct vm_area_struct *vma);
+};
+
+struct vm_special_mapping {
+    const char *name;
+};
+
 struct vm_area_struct {
     union {
         struct {
@@ -301,7 +311,9 @@ struct vm_area_struct {
     struct rb_node vm_rb;
     struct mm_struct *vm_mm;
     long unsigned int vm_flags;
+    const struct vm_operations_struct *vm_ops;
     struct file *vm_file;
+    void *vm_private_data;
 };
 
 typedef unsigned int __kernel_gid32_t;

diff --git a/pkg/ebpf/initialization/kconfig.go b/pkg/ebpf/initialization/kconfig.go
@@ -1,7 +1,6 @@
 package initialization
 
 import (
-	"github.com/aquasecurity/libbpfgo/helpers"
 	"github.com/aquasecurity/tracee/pkg/errfmt"
 	"github.com/aquasecurity/tracee/pkg/logger"
 	"github.com/aquasecurity/tracee/pkg/utils/environment"
@@ -11,7 +10,7 @@ import (
 // Add here all kconfig variables used within tracee.bpf.c
 const (
 	CONFIG_ARCH_HAS_SYSCALL_WRAPPER environment.KernelConfigOption = iota + environment.CUSTOM_OPTION_START
-	CONFIG_MMU                      helpers.KernelConfigOption     = iota + helpers.CUSTOM_OPTION_START
+	CONFIG_MMU                      environment.KernelConfigOption = iota + environment.CUSTOM_OPTION_START
 )
 
 var kconfigUsed = map[environment.KernelConfigOption]string{
@@ -36,7 +35,7 @@ func LoadKconfigValues(kc *environment.KernelConfig) (map[environment.KernelConf
 			values[key] = environment.UNDEFINED
 		}
 		values[CONFIG_ARCH_HAS_SYSCALL_WRAPPER] = environment.BUILTIN // assume CONFIG_ARCH_HAS_SYSCALL_WRAPPER is a BUILTIN option
-		values[CONFIG_MMU] = helpers.BUILTIN                          // assume CONFIG_MMU is a BUILTIN option
+		values[CONFIG_MMU] = environment.BUILTIN                      // assume CONFIG_MMU is a BUILTIN option
 	} else {
 		for key := range kconfigUsed {
 			values[key] = kc.GetValue(key) // undefined, builtin OR module

diff --git a/tests/e2e-inst-signatures/e2e-check_syscall_source.go b/tests/e2e-inst-signatures/e2e-check_syscall_source.go
@@ -3,7 +3,7 @@ package main
 import (
 	"fmt"
 
-	libbfgo "github.com/aquasecurity/libbpfgo/helpers"
+	libbpfgo "github.com/aquasecurity/libbpfgo/helpers"
 
 	"github.com/aquasecurity/tracee/signatures/helpers"
 	"github.com/aquasecurity/tracee/types/detect"
@@ -24,11 +24,11 @@ func (sig *e2eCheckSyscallSource) Init(ctx detect.SignatureContext) error {
 
 	// Find if this system uses maple trees to manage VMAs.
 	// If so we don't expect any check_syscall_source event to be submitted.
-	ksyms, err := libbfgo.NewKernelSymbolTable()
+	ksyms, err := libbpfgo.NewKernelSymbolsMap()
 	if err != nil {
 		return err
 	}
-	_, err = ksyms.GetSymbolByName("mt_find")
+	_, err = ksyms.GetSymbolByName("system", "mt_find")
 	if err != nil {
 		sig.hasMapleTree = false
 	} else {