github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-09-27 11:02:03 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

bpf: Skip unsettled links in link iterator

Browse Source 
bpf_link_prime() inserts a link into link_idr before anon_inode_getfile()
succeeds and before bpf_link_settle() publishes the ID in link->id.
bpf_link_by_id() treats such an ID-zero link as unsettled, but the link
iterator takes a reference without this check.

If anon_inode_getfile() then fails, the creator removes the ID and frees
its still-private link directly.  The iterator is left with a dangling
reference and its next bpf_link_put() accesses freed memory.

Treat ID-zero entries as transient in bpf_link_get_curr_or_next(), just as
bpf_link_by_id() does.

  BUG: KASAN: slab-use-after-free in bpf_link_put
  Write of size 8 by task exp/384
  Call Trace:
  bpf_link_put                    kernel/bpf/syscall.c:3372
  bpf_link_seq_next               kernel/bpf/link_iter.c:33
  bpf_seq_read                    kernel/bpf/bpf_iter.c:158
  vfs_read                        fs/read_write.c:572
  ksys_read                       fs/read_write.c:716
  do_syscall_64                   arch/x86/entry/syscall_64.c:84
  entry_SYSCALL_64_after_hwframe  arch/x86/entry/entry_64.S:121
  Kernel panic - not syncing: KASAN: panic_on_warn set ...

Fixes: 9f88361273 ("bpf: Add bpf_link iterator")
Reported-by: Xiang Mei <xmei5@asu.edu>
Signed-off-by: Weiming Shi <bestswngs@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20260914170206.170723-2-bestswngs@gmail.com
This commit is contained in:
Weiming Shi 2026-09-15 01:02:07 +08:00 committed by Andrii Nakryiko
parent 70504de0bb
commit 50e80e2bb5
1 changed files with 4 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

5
kernel/bpf/syscall.c
View File

@ -6042,7 +6042,10 @@ struct bpf_link *bpf_link_get_curr_or_next(u32 *id)
again:
link = idr_get_next(&link_idr, id);
if (link) {
link = bpf_link_inc_not_zero(link);
if (link->id)
link = bpf_link_inc_not_zero(link);
else
link = ERR_PTR(-EAGAIN);
if (IS_ERR(link)) {
(*id)++;
goto again;