diff mbox series

[bpf,v2,6/9] bpf: Only allow sleepable program for resched-able iterator

Message ID 20220810080538.1845898-7-houtao@huaweicloud.com (mailing list archive)
State Accepted
Commit d247049f4fd088e4e40294819a932a6057b3632c
Delegated to: BPF
Headers show
Series fixes for bpf map iterator | expand

Checks

Context Check Description
bpf/vmtest-bpf-PR fail PR summary
netdev/tree_selection success Clearly marked for bpf
netdev/fixes_present success Fixes tag present in non-next series
netdev/subject_prefix success Link
netdev/cover_letter success Series has a cover letter
netdev/patch_count success Link
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 2 this patch: 2
netdev/cc_maintainers warning 2 maintainers not CCed: song@kernel.org martin.lau@linux.dev
netdev/build_clang success Errors and warnings before: 5 this patch: 5
netdev/module_param success Was 0 now: 0
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 2 this patch: 2
netdev/checkpatch warning WARNING: line length of 92 exceeds 80 columns
netdev/kdoc success Errors and warnings before: 0 this patch: 0
netdev/source_inline fail Was 0 now: 1
bpf/vmtest-bpf-VM_Test-1 success Logs for Kernel LATEST on ubuntu-latest with gcc
bpf/vmtest-bpf-VM_Test-2 success Logs for Kernel LATEST on ubuntu-latest with llvm-16
bpf/vmtest-bpf-VM_Test-3 fail Logs for Kernel LATEST on z15 with gcc

Commit Message

Hou Tao Aug. 10, 2022, 8:05 a.m. UTC 
From: Hou Tao <houtao1@huawei.com>

When a sleepable program is attached to a hash map iterator, might_fault()
will report "BUG: sleeping function called from invalid context..." if
CONFIG_DEBUG_ATOMIC_SLEEP is enabled. The reason is that rcu_read_lock()
is held in bpf_hash_map_seq_next() and won't be released until all elements
are traversed or bpf_hash_map_seq_stop() is called.

Fixing it by reusing BPF_ITER_RESCHED to indicate that only non-sleepable
program is allowed for iterator without BPF_ITER_RESCHED. We can revise
bpf_iter_link_attach() later if there are other conditions which may
cause rcu_read_lock() or spin_lock() issues.

Signed-off-by: Hou Tao <houtao1@huawei.com>
Acked-by: Yonghong Song <yhs@fb.com>
---
 kernel/bpf/bpf_iter.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/kernel/bpf/bpf_iter.c b/kernel/bpf/bpf_iter.c
index 4b112aa8bba3..97bb57493ed5 100644
--- a/kernel/bpf/bpf_iter.c
+++ b/kernel/bpf/bpf_iter.c
@@ -68,13 +68,18 @@  static void bpf_iter_done_stop(struct seq_file *seq)
 	iter_priv->done_stop = true;
 }
 
+static inline bool bpf_iter_target_support_resched(const struct bpf_iter_target_info *tinfo)
+{
+	return tinfo->reg_info->feature & BPF_ITER_RESCHED;
+}
+
 static bool bpf_iter_support_resched(struct seq_file *seq)
 {
 	struct bpf_iter_priv_data *iter_priv;
 
 	iter_priv = container_of(seq->private, struct bpf_iter_priv_data,
 				 target_private);
-	return iter_priv->tinfo->reg_info->feature & BPF_ITER_RESCHED;
+	return bpf_iter_target_support_resched(iter_priv->tinfo);
 }
 
 /* maximum visited objects before bailing out */
@@ -542,6 +547,10 @@  int bpf_iter_link_attach(const union bpf_attr *attr, bpfptr_t uattr,
 	if (!tinfo)
 		return -ENOENT;
 
+	/* Only allow sleepable program for resched-able iterator */
+	if (prog->aux->sleepable && !bpf_iter_target_support_resched(tinfo))
+		return -EINVAL;
+
 	link = kzalloc(sizeof(*link), GFP_USER | __GFP_NOWARN);
 	if (!link)
 		return -ENOMEM;