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| author |   John Ogness <john.ogness@linutronix.de> | 2020-09-14 11:54:03 +0206 |
|---|---|---|
| committer |   Petr Mladek <pmladek@suse.com> | 2020-09-15 14:42:09 +0200 |
| commit | e7c1fe21046a024a5a9ef46e3752521afc1ada7b (patch) | |
| tree | b175c311c3fde2b4b5b33095e03c0c42ef8a4fac /kernel/printk/printk_ringbuffer.c | |
| parent | printk: ringbuffer: fix setting state in desc_read() (diff) | |
| download | linux-dev-e7c1fe21046a024a5a9ef46e3752521afc1ada7b.tar.xz linux-dev-e7c1fe21046a024a5a9ef46e3752521afc1ada7b.zip | |
printk: ringbuffer: avoid memcpy() on state_var
@state_var is copied as part of the descriptor copying via
memcpy(). This is not allowed because @state_var is an atomic type,
which in some implementations may contain a spinlock.
Avoid using memcpy() with @state_var by explicitly copying the other
fields of the descriptor. @state_var is set using atomic set
operator before returning.
Fixes: b6cf8b3f3312 ("printk: add lockless ringbuffer")
Signed-off-by: John Ogness <john.ogness@linutronix.de>
Reviewed-by: Petr Mladek <pmladek@suse.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
Link: https://lore.kernel.org/r/20200914094803.27365-2-john.ogness@linutronix.de
Diffstat (limited to 'kernel/printk/printk_ringbuffer.c')
| -rw-r--r-- | kernel/printk/printk_ringbuffer.c | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/kernel/printk/printk_ringbuffer.c b/kernel/printk/printk_ringbuffer.c index 88f7dd4cb0c1..11b860ad5264 100644 --- a/kernel/printk/printk_ringbuffer.c +++ b/kernel/printk/printk_ringbuffer.c @@ -412,9 +412,14 @@ static enum desc_state desc_read(struct prb_desc_ring *desc_ring, /* * Copy the descriptor data. The data is not valid until the - * state has been re-checked. + * state has been re-checked. A memcpy() for all of @desc + * cannot be used because of the atomic_t @state_var field. */ - memcpy(desc_out, desc, sizeof(*desc_out)); /* LMM(desc_read:C) */ + memcpy(&desc_out->info, &desc->info, sizeof(desc_out->info)); /* LMM(desc_read:C) */ + memcpy(&desc_out->text_blk_lpos, &desc->text_blk_lpos, + sizeof(desc_out->text_blk_lpos)); /* also part of desc_read:C */ + memcpy(&desc_out->dict_blk_lpos, &desc->dict_blk_lpos, + sizeof(desc_out->dict_blk_lpos)); /* also part of desc_read:C */ /* * 1. Guarantee the descriptor content is loaded before re-checking |