Re: [PATCH] ring buffer: propagate __rb_map_vma return value to caller
From: Steven Rostedt <rostedt@goodmis.org>
Date: 2025-10-08 16:09:20
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linux-kernel-mentees, lkml
On Tue, 7 Oct 2025 22:42:56 +0530 Ankit Khushwaha [off-list ref] wrote: Note, tracing subsystem expects the subject to start with a capital letter: ring buffer: Propagate __rb_map_vma return value to caller
quoted hunk ↗ jump to hunk
The return value from `__rb_map_vma()`, which rejects writable or executable mappings (VM_WRITE, VM_EXEC, or !VM_MAYSHARE), was being ignored. As a result the caller of `__rb_map_vma` always returned 0 even when the mapping had actually failed, allowing it to proceed with an invalid VMA. Reported-by: syzbot+ddc001b92c083dbf2b97@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?id=194151be8eaebd826005329b2e123aecae714bdb Signed-off-by: Ankit Khushwaha <redacted> --- #syz test: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git 4ff71af020ae --- kernel/trace/ring_buffer.c | 2 ++ 1 file changed, 2 insertions(+)diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 43460949ad3f..4efb90364f48 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c@@ -7271,6 +7271,8 @@ int ring_buffer_map(struct trace_buffer *buffer, int cpu, cpu_buffer->subbuf_ids = NULL; rb_free_meta_page(cpu_buffer); atomic_dec(&cpu_buffer->resize_disabled); + /* VM failed to be mapped */
No need to add the comment. It's obvious what happened.
+ return err;
Don't return here.
} return 0;
Change this to: return err; as after that if statement, err will be 0 on success or the value you want to return. -- Steve