1 files changed, 198 insertions, 17 deletions

diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c
index da3d328f5c15..77ba03216c09 100644
--- a/kernel/bpf/stackmap.c
+++ b/kernel/bpf/stackmap.c
@@ -9,6 +9,7 @@
 #include <linux/perf_event.h>
 #include <linux/btf_ids.h>
 #include <linux/buildid.h>
+#include <linux/mmap_lock.h>
 #include "percpu_freelist.h"
 #include "mmap_unlock_work.h"
 
@@ -152,6 +153,180 @@ static int fetch_build_id(struct vm_area_struct *vma, unsigned char *build_id, b
 			 : build_id_parse_nofault(vma, build_id, NULL);
 }
 
+static inline void stack_map_build_id_set_ip(struct bpf_stack_build_id *id)
+{
+	id->status = BPF_STACK_BUILD_ID_IP;
+	memset(id->build_id, 0, BUILD_ID_SIZE_MAX);
+}
+
+static inline u64 stack_map_build_id_offset(unsigned long vm_pgoff,
+					    unsigned long vm_start, u64 ip)
+{
+	return (vm_pgoff << PAGE_SHIFT) + ip - vm_start;
+}
+
+static inline void stack_map_build_id_set_valid(struct bpf_stack_build_id *id,
+						u64 offset,
+						const unsigned char *build_id)
+{
+	id->status = BPF_STACK_BUILD_ID_VALID;
+	id->offset = offset;
+	if (id->build_id != build_id)
+		memcpy(id->build_id, build_id, BUILD_ID_SIZE_MAX);
+}
+
+struct stack_map_vma_lock {
+	struct vm_area_struct *vma;
+	struct mm_struct *mm;
+};
+
+/*
+ * Acquire a stable read-side reference on the VMA covering @ip.
+ *
+ * With CONFIG_PER_VMA_LOCK=y this returns a VMA with its per-VMA read
+ * lock held and mmap_lock dropped, so the caller may sleep.
+ *
+ * With CONFIG_PER_VMA_LOCK=n it returns a VMA with mmap_lock still
+ * held; the caller must snapshot any fields it needs and pin vm_file
+ * with get_file() before stack_map_unlock_vma() drops mmap_lock, as
+ * the VMA may be split, merged, or freed after that.
+ *
+ * Returns NULL on failure, in which case no lock is held.
+ */
+static struct vm_area_struct *
+stack_map_lock_vma(struct stack_map_vma_lock *lock, unsigned long ip)
+{
+	struct mm_struct *mm = lock->mm;
+	struct vm_area_struct *vma;
+
+	/* noop under !CONFIG_PER_VMA_LOCK */
+	vma = lock_vma_under_rcu(mm, ip);
+	if (vma) {
+		lock->vma = vma;
+		return vma;
+	}
+
+	/*
+	 * Taking mmap_read_lock() is unsafe here, because the caller BPF
+	 * program might already hold it, causing a deadlock.
+	 */
+	if (!mmap_read_trylock(mm))
+		return NULL;
+
+	vma = vma_lookup(mm, ip);
+	if (!vma) {
+		mmap_read_unlock(mm);
+		return NULL;
+	}
+
+#ifdef CONFIG_PER_VMA_LOCK
+	if (!vma_start_read_locked(vma)) {
+		mmap_read_unlock(mm);
+		return NULL;
+	}
+	mmap_read_unlock(mm);
+#endif
+
+	lock->vma = vma;
+	return vma;
+}
+
+static void stack_map_unlock_vma(struct stack_map_vma_lock *lock)
+{
+#ifdef CONFIG_PER_VMA_LOCK
+	vma_end_read(lock->vma);
+#else
+	mmap_read_unlock(lock->mm);
+#endif
+	lock->vma = NULL;
+}
+
+static void stack_map_get_build_id_offset_sleepable(struct bpf_stack_build_id *id_offs,
+						    u32 trace_nr)
+{
+	struct mm_struct *mm = current->mm;
+	struct stack_map_vma_lock lock = { .mm = mm };
+	struct {
+		struct file *file;
+		const unsigned char *build_id;
+		unsigned long vm_start;
+		unsigned long vm_end;
+		unsigned long vm_pgoff;
+	} cache = {};
+	unsigned long vm_pgoff, vm_start, vm_end;
+	struct vm_area_struct *vma;
+	struct file *file;
+	u64 offset;
+	u64 ip;
+
+	for (u32 i = 0; i < trace_nr; i++) {
+		ip = READ_ONCE(id_offs[i].ip);
+
+		/*
+		 * Range cache fast path: if ip falls within the previously
+		 * resolved VMA range, reuse the cache build_id without
+		 * re-acquiring the VMA lock.
+		 */
+		if (cache.build_id && ip >= cache.vm_start && ip < cache.vm_end) {
+			offset = stack_map_build_id_offset(cache.vm_pgoff, cache.vm_start, ip);
+			stack_map_build_id_set_valid(&id_offs[i], offset, cache.build_id);
+			continue;
+		}
+
+		vma = stack_map_lock_vma(&lock, ip);
+		if (!vma) {
+			stack_map_build_id_set_ip(&id_offs[i]);
+			continue;
+		}
+		if (vma_is_anonymous(vma) || !vma->vm_file) {
+			stack_map_build_id_set_ip(&id_offs[i]);
+			stack_map_unlock_vma(&lock);
+			continue;
+		}
+
+		file = vma->vm_file;
+		vm_pgoff = vma->vm_pgoff;
+		vm_start = vma->vm_start;
+		vm_end = vma->vm_end;
+		offset = stack_map_build_id_offset(vm_pgoff, vm_start, ip);
+
+		/*
+		 * Same backing file as previous (e.g. different VMAs
+		 * of the same ELF binary). Reuse the cache build_id.
+		 */
+		if (file == cache.file) {
+			stack_map_unlock_vma(&lock);
+			stack_map_build_id_set_valid(&id_offs[i], offset, cache.build_id);
+			cache.vm_start = vm_start;
+			cache.vm_end = vm_end;
+			cache.vm_pgoff = vm_pgoff;
+			continue;
+		}
+
+		file = get_file(file);
+		stack_map_unlock_vma(&lock);
+
+		/* build_id_parse_file() may block on filesystem reads */
+		if (build_id_parse_file(file, id_offs[i].build_id, NULL)) {
+			stack_map_build_id_set_ip(&id_offs[i]);
+			fput(file);
+			continue;
+		}
+
+		stack_map_build_id_set_valid(&id_offs[i], offset, id_offs[i].build_id);
+		if (cache.file)
+			fput(cache.file);
+		cache.file = file;
+		cache.build_id = id_offs[i].build_id;
+		cache.vm_start = vm_start;
+		cache.vm_end = vm_end;
+		cache.vm_pgoff = vm_pgoff;
+	}
+
+	if (cache.file)
+		fput(cache.file);
+}
+
 /*
  * Expects all id_offs[i].ip values to be set to correct initial IPs.
  * They will be subsequently:
@@ -165,44 +340,50 @@ static int fetch_build_id(struct vm_area_struct *vma, unsigned char *build_id, b
 static void stack_map_get_build_id_offset(struct bpf_stack_build_id *id_offs,
 					  u32 trace_nr, bool user, bool may_fault)
 {
-	int i;
 	struct mmap_unlock_irq_work *work = NULL;
 	bool irq_work_busy = bpf_mmap_unlock_get_irq_work(&work);
+	bool has_user_ctx = user && current && current->mm;
 	struct vm_area_struct *vma, *prev_vma = NULL;
-	const char *prev_build_id;
+	const unsigned char *prev_build_id = NULL;
+	int i;
+
+	if (may_fault && has_user_ctx) {
+		stack_map_get_build_id_offset_sleepable(id_offs, trace_nr);
+		return;
+	}
 
 	/* If the irq_work is in use, fall back to report ips. Same
 	 * fallback is used for kernel stack (!user) on a stackmap with
 	 * build_id.
 	 */
-	if (!user || !current || !current->mm || irq_work_busy ||
-	    !mmap_read_trylock(current->mm)) {
+	if (!has_user_ctx || irq_work_busy || !mmap_read_trylock(current->mm)) {
 		/* cannot access current->mm, fall back to ips */
-		for (i = 0; i < trace_nr; i++) {
-			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
-			memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
-		}
+		for (i = 0; i < trace_nr; i++)
+			stack_map_build_id_set_ip(&id_offs[i]);
 		return;
 	}
 
 	for (i = 0; i < trace_nr; i++) {
 		u64 ip = READ_ONCE(id_offs[i].ip);
+		u64 offset;
 
-		if (range_in_vma(prev_vma, ip, ip)) {
+		if (prev_build_id && range_in_vma(prev_vma, ip, ip)) {
 			vma = prev_vma;
-			memcpy(id_offs[i].build_id, prev_build_id, BUILD_ID_SIZE_MAX);
-			goto build_id_valid;
+			offset = stack_map_build_id_offset(vma->vm_pgoff, vma->vm_start, ip);
+			stack_map_build_id_set_valid(&id_offs[i], offset, prev_build_id);
+			continue;
 		}
 		vma = find_vma(current->mm, ip);
-		if (!vma || fetch_build_id(vma, id_offs[i].build_id, may_fault)) {
+		if (!vma || vma_is_anonymous(vma) ||
+		    fetch_build_id(vma, id_offs[i].build_id, may_fault)) {
 			/* per entry fall back to ips */
-			id_offs[i].status = BPF_STACK_BUILD_ID_IP;
-			memset(id_offs[i].build_id, 0, BUILD_ID_SIZE_MAX);
+			stack_map_build_id_set_ip(&id_offs[i]);
+			prev_vma = vma;
+			prev_build_id = NULL;
 			continue;
 		}
-build_id_valid:
-		id_offs[i].offset = (vma->vm_pgoff << PAGE_SHIFT) + ip - vma->vm_start;
-		id_offs[i].status = BPF_STACK_BUILD_ID_VALID;
+		offset = stack_map_build_id_offset(vma->vm_pgoff, vma->vm_start, ip);
+		stack_map_build_id_set_valid(&id_offs[i], offset, id_offs[i].build_id);
 		prev_vma = vma;
 		prev_build_id = id_offs[i].build_id;
 	}