[PATCH OLK-6.6 0/2] CVE-2025-68378
Arnaud Lecomte (2): bpf: Refactor stack map trace depth calculation into helper function bpf: Fix stackmap overflow check in __bpf_get_stackid() kernel/bpf/stackmap.c | 64 +++++++++++++++++++++++++++---------------- 1 file changed, 41 insertions(+), 23 deletions(-) -- 2.34.1
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From: Arnaud Lecomte <contact@arnaud-lcm.com> mainline inclusion from mainline-v6.19-rc1 commit e17d62fedd10ae56e2426858bd0757da544dbc73 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/12748 CVE: CVE-2025-68378 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- Extract the duplicated maximum allowed depth computation for stack traces stored in BPF stacks from bpf_get_stackid() and __bpf_get_stack() into a dedicated stack_map_calculate_max_depth() helper function. This unifies the logic for: - The max depth computation - Enforcing the sysctl_perf_event_max_stack limit No functional changes for existing code paths. 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/20251025192858.31424-1-contact@arnaud-lcm.com Conflicts: kernel/bpf/stackmap.c [ctx conflicts] Signed-off-by: Pu Lehui <pulehui@huawei.com> --- kernel/bpf/stackmap.c | 47 +++++++++++++++++++++++++++++-------------- 1 file changed, 32 insertions(+), 15 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index a330f38ae733..590cc9a91a0b 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -42,6 +42,28 @@ static inline int stack_map_data_size(struct bpf_map *map) sizeof(struct bpf_stack_build_id) : sizeof(u64); } +/** + * stack_map_calculate_max_depth - Calculate maximum allowed stack trace depth + * @size: Size of the buffer/map value in bytes + * @elem_size: Size of each stack trace element + * @flags: BPF stack trace flags (BPF_F_USER_STACK, BPF_F_USER_BUILD_ID, ...) + * + * Return: Maximum number of stack trace entries that can be safely stored + */ +static u32 stack_map_calculate_max_depth(u32 size, u32 elem_size, u64 flags) +{ + u32 skip = flags & BPF_F_SKIP_FIELD_MASK; + u32 max_depth; + u32 curr_sysctl_max_stack = READ_ONCE(sysctl_perf_event_max_stack); + + max_depth = size / elem_size; + max_depth += skip; + if (max_depth > curr_sysctl_max_stack) + return curr_sysctl_max_stack; + + return max_depth; +} + static int prealloc_elems_and_freelist(struct bpf_stack_map *smap) { u64 elem_size = sizeof(struct stack_map_bucket) + @@ -283,20 +305,17 @@ static long __bpf_get_stackid(struct bpf_map *map, BPF_CALL_3(bpf_get_stackid, struct pt_regs *, regs, struct bpf_map *, map, u64, flags) { - u32 max_depth = map->value_size / stack_map_data_size(map); - u32 skip = flags & BPF_F_SKIP_FIELD_MASK; + u32 elem_size = stack_map_data_size(map); bool user = flags & BPF_F_USER_STACK; struct perf_callchain_entry *trace; bool kernel = !user; + u32 max_depth; if (unlikely(flags & ~(BPF_F_SKIP_FIELD_MASK | BPF_F_USER_STACK | BPF_F_FAST_STACK_CMP | BPF_F_REUSE_STACKID))) return -EINVAL; - max_depth += skip; - if (max_depth > sysctl_perf_event_max_stack) - max_depth = sysctl_perf_event_max_stack; - + max_depth = stack_map_calculate_max_depth(map->value_size, elem_size, flags); trace = get_perf_callchain(regs, 0, kernel, user, max_depth, false, false); @@ -389,7 +408,7 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, struct perf_callchain_entry *trace_in, void *buf, u32 size, u64 flags) { - u32 trace_nr, copy_len, elem_size, num_elem, max_depth; + u32 trace_nr, copy_len, elem_size, max_depth; bool user_build_id = flags & BPF_F_USER_BUILD_ID; bool crosstask = task && task != current; u32 skip = flags & BPF_F_SKIP_FIELD_MASK; @@ -422,18 +441,17 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, goto clear; } - num_elem = size / elem_size; - max_depth = num_elem + skip; - if (sysctl_perf_event_max_stack < max_depth) - max_depth = sysctl_perf_event_max_stack; + max_depth = stack_map_calculate_max_depth(size, elem_size, flags); - if (trace_in) + if (trace_in) { trace = trace_in; - else if (kernel && task) + trace->nr = min_t(u32, trace->nr, max_depth); + } else if (kernel && task) { trace = get_callchain_entry_for_task(task, max_depth); - else + } else { trace = get_perf_callchain(regs, 0, kernel, user, max_depth, crosstask, false); + } if (unlikely(!trace)) goto err_fault; @@ -441,7 +459,6 @@ static long __bpf_get_stack(struct pt_regs *regs, struct task_struct *task, goto err_fault; trace_nr = trace->nr - skip; - trace_nr = (trace_nr <= num_elem) ? trace_nr : num_elem; copy_len = trace_nr * elem_size; ips = trace->ip + skip; -- 2.34.1
From: Arnaud Lecomte <contact@arnaud-lcm.com> mainline inclusion from mainline-v6.19-rc1 commit 23f852daa4bab4d579110e034e4d513f7d490846 category: bugfix bugzilla: https://atomgit.com/src-openeuler/kernel/issues/12748 CVE: CVE-2025-68378 Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- 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 Conflicts: kernel/bpf/stackmap.c [Make variable nr definition up to avoid build warning] Signed-off-by: Pu Lehui <pulehui@huawei.com> --- kernel/bpf/stackmap.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-) diff --git a/kernel/bpf/stackmap.c b/kernel/bpf/stackmap.c index 590cc9a91a0b..7f8adb1dc152 100644 --- a/kernel/bpf/stackmap.c +++ b/kernel/bpf/stackmap.c @@ -237,8 +237,8 @@ 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, max_depth; u32 skip = flags & BPF_F_SKIP_FIELD_MASK; - u32 hash, id, trace_nr, trace_len; bool user = flags & BPF_F_USER_STACK; u64 *ips; bool hash_matches; @@ -247,7 +247,8 @@ 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); @@ -353,7 +354,7 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, struct perf_event *event = ctx->event; struct perf_callchain_entry *trace; bool kernel, user; - __u64 nr_kernel; + __u64 nr_kernel, nr; int ret; /* perf_sample_data doesn't have callchain, use bpf_get_stackid */ @@ -373,15 +374,11 @@ BPF_CALL_3(bpf_get_stackid_pe, struct bpf_perf_event_data_kern *, ctx, return -EFAULT; nr_kernel = count_kernel_ip(trace); + 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; @@ -392,6 +389,10 @@ 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; } -- 2.34.1
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