6.6-stable review patch. If anyone has any objections, please let me know.
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From: Harald Freudenberger freude@linux.ibm.com
[ Upstream commit 95c0f5c3b8bb7acdc5c4f04bc6a7d3f40d319e9e ]
When there are rng sources registering at the hwrng core via hwrng_register() a struct hwrng is delivered. There is a quality field in there which is used to decide which of the registered hw rng sources will be used by the hwrng core.
With commit 16bdbae39428 ("hwrng: core - treat default_quality as a maximum and default to 1024") there came in a new default of 1024 in case this field is empty and all the known hw rng sources at that time had been reworked to not fill this field and thus use the default of 1024.
The code choosing the 'better' hw rng source during registration of a new hw rng source has never been adapted to this and thus used 0 if the hw rng implementation does not fill the quality field. So when two rng sources register, one with 0 (meaning 1024) and the other one with 999, the 999 hw rng will be chosen.
As the later invoked function hwrng_init() anyway adjusts the quality field of the hw rng source, this adjustment is now done during registration of this new hw rng source.
Tested on s390 with two hardware rng sources: crypto cards and trng true random generator device driver.
Fixes: 16bdbae39428 ("hwrng: core - treat default_quality as a maximum and default to 1024") Reported-by: Christian Rund Christian.Rund@de.ibm.com Suggested-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Harald Freudenberger freude@linux.ibm.com Signed-off-by: Herbert Xu herbert@gondor.apana.org.au Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/char/hw_random/core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-)
diff --git a/drivers/char/hw_random/core.c b/drivers/char/hw_random/core.c index a3bbdd6e60fca..a182fe794f985 100644 --- a/drivers/char/hw_random/core.c +++ b/drivers/char/hw_random/core.c @@ -174,7 +174,6 @@ static int hwrng_init(struct hwrng *rng) reinit_completion(&rng->cleanup_done);
skip_init: - rng->quality = min_t(u16, min_t(u16, default_quality, 1024), rng->quality ?: 1024); current_quality = rng->quality; /* obsolete */
return 0; @@ -563,6 +562,9 @@ int hwrng_register(struct hwrng *rng) complete(&rng->cleanup_done); init_completion(&rng->dying);
+ /* Adjust quality field to always have a proper value */ + rng->quality = min_t(u16, min_t(u16, default_quality, 1024), rng->quality ?: 1024); + if (!current_rng || (!cur_rng_set_by_user && rng->quality > current_rng->quality)) { /*