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bpf: map_seq_next should always increase position index 

If seq_file .next fuction does not change position index,
read after some lseek can generate an unexpected output.

See also: https://bugzilla.kernel.org/show_bug.cgi?id=206283

v1 -> v2: removed missed increment in end of function

Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/eca84fdd-c374-a154-d874-6c7b55fc3bc4@virtuozzo.com
alistair/sensors
Vasily Averin 2020-01-25 12:10:02 +03:00 committed by Daniel Borkmann
parent 07fdbee134
commit 90435a7891
1 changed files with 1 additions and 2 deletions
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3
kernel/bpf/inode.c
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@ -196,6 +196,7 @@ static void *map_seq_next(struct seq_file *m, void *v, loff_t *pos)
void *key = map_iter(m)->key;
void *prev_key;
(*pos)++;
if (map_iter(m)->done)
return NULL;
@ -208,8 +209,6 @@ static void *map_seq_next(struct seq_file *m, void *v, loff_t *pos)
map_iter(m)->done = true;
return NULL;
}
++(*pos);
return key;
}