Re: [PATCH mm] VFS: seq_file: ensure ->from is valid.
From: Jann Horn <jannh@google.com>
Date: 2018-07-07 03:50:28
Also in:
linux-fsdevel, lkml
On Sat, Jul 7, 2018 at 5:29 AM NeilBrown [off-list ref] wrote:
Previous patch ("VFS: simplify seq_file iteration code and interface")
removed code to set ->from to zero when ->count is zero, as ->from is
dead at that time. However it didn't ensure ->from was set properly
whenever ->count becomes non-zero.
This can only happen when ->show() is called. Of the three places it
is called one already has ->from set to zero. The other two are
fixed by setting from to zero after fully flushing the buffer (at which
point ->count will also be zero).
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: NeilBrown <redacted>Tested-by: Jann Horn <jannh@google.com>
quoted hunk ↗ jump to hunk
--- fs/seq_file.c | 1 + 1 file changed, 1 insertion(+)diff --git a/fs/seq_file.c b/fs/seq_file.c index fd82585ab50f..1dea7a8a5255 100644 --- a/fs/seq_file.c +++ b/fs/seq_file.c@@ -220,6 +220,7 @@ ssize_t seq_read(struct file *file, char __user *buf, size_t size, loff_t *ppos) goto Done; } /* we need at least one record in buffer */ + m->from = 0; p = m->op->start(m, &m->index); while (1) { err = PTR_ERR(p);
This looks correct to me. I have also tested that with this patch applied, my crasher doesn't work anymore. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html