6.18-stable review patch. If anyone has any objections, please let me know.
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From: Arnaud Lecomte contact@arnaud-lcm.com
[ Upstream commit 23f852daa4bab4d579110e034e4d513f7d490846 ]
Syzkaller reported a KASAN slab-out-of-bounds write in __bpf_get_stackid() when copying stack trace data. The issue occurs when the perf trace contains more stack entries than the stack map bucket can hold, leading to an out-of-bounds write in the bucket's data array.
Fixes: ee2a098851bf ("bpf: Adjust BPF stack helper functions to accommodate skip > 0") Reported-by: syzbot+c9b724fbb41cf2538b7b@syzkaller.appspotmail.com Signed-off-by: Arnaud Lecomte contact@arnaud-lcm.com Signed-off-by: Andrii Nakryiko andrii@kernel.org Acked-by: Yonghong Song yonghong.song@linux.dev Acked-by: Song Liu song@kernel.org Link: https://lore.kernel.org/bpf/20251025192941.1500-1-contact@arnaud-lcm.com
Closes: https://syzkaller.appspot.com/bug?extid=c9b724fbb41cf2538b7b Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/stackmap.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-)
diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 5e9ad050333c2..2365541c81dd1 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -251,8 +251,8 @@ static long __bpf_get_stackid(struct bpf_map *map, { struct bpf_stack_map *smap = container_of(map, struct bpf_stack_map, map); struct stack_map_bucket *bucket, *new_bucket, *old_bucket; + u32 hash, id, trace_nr, trace_len, i, max_depth; u32 skip = flags & BPF_F_SKIP_FIELD_MASK; - u32 hash, id, trace_nr, trace_len, i; bool user = flags & BPF_F_USER_STACK; u64 *ips; bool hash_matches; @@ -261,7 +261,8 @@ static long __bpf_get_stackid(struct bpf_map *map, /* skipping more than usable stack trace */ return -EFAULT;
- trace_nr = trace->nr - skip; + max_depth = stack_map_calculate_max_depth(map->value_size, stack_map_data_size(map), flags); + trace_nr = min_t(u32, trace->nr - skip, max_depth - skip); trace_len = trace_nr * sizeof(u64); ips = trace->ip + skip; hash = jhash2((u32 *)ips, trace_len / sizeof(u32), 0); @@ -390,15 +391,11 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, return -EFAULT;
nr_kernel = count_kernel_ip(trace); + __u64 nr = trace->nr; /* save original */
if (kernel) { - __u64 nr = trace->nr; - trace->nr = nr_kernel; ret = __bpf_get_stackid(map, trace, flags); - - /* restore nr */ - trace->nr = nr; } else { /* user */ u64 skip = flags & BPF_F_SKIP_FIELD_MASK;
@@ -409,6 +406,10 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, flags = (flags & ~BPF_F_SKIP_FIELD_MASK) | skip; ret = __bpf_get_stackid(map, trace, flags); } + + /* restore nr */ + trace->nr = nr; + return ret; }