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net/mlx4: avoid GCC 10 __bad_copy_from() false positive

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mlx4_init_user_cqes() fills a scratch buffer with the CQE
initialization pattern and then copies from that buffer to userspace.

In the single-copy path, the copy length is array_size(entries,
cqe_size), but the scratch buffer is allocated with PAGE_SIZE. GCC 10
does not carry the branch invariant strongly enough through the object
size checks and falsely triggers __bad_copy_from().

Size the scratch buffer to the actual copy length for the active path,
keep array_size() for the single-copy case, and retain a WARN_ON_ONCE()
guard for the PAGE_SIZE invariant before allocating the buffer.

Fixes: f69bf5dee7 ("net/mlx4: Use array_size() helper in copy_to_user()")
Signed-off-by: Yao Sang <sangyao@kylinos.cn>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Yao Sang 2026-06-03 14:10:44 +08:00 • committed by Jakub Kicinski
commit 2365343f4a
1 changed files with 8 additions and 1 deletions
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9
drivers/net/ethernet/mellanox/mlx4/cq.c
View file

@ -290,6 +290,7 @@ static void mlx4_cq_free_icm(struct mlx4_dev *dev, int cqn)
static int mlx4_init_user_cqes(void *buf, int entries, int cqe_size)
{
int entries_per_copy = PAGE_SIZE / cqe_size;
size_t copy_bytes;
void *init_ents;
int err = 0;
int i;
@ -314,8 +315,14 @@ static int mlx4_init_user_cqes(void *buf, int entries, int cqe_size)
buf += PAGE_SIZE;
}
} else {
copy_bytes = array_size(entries, cqe_size);
if (WARN_ON_ONCE(copy_bytes > PAGE_SIZE)) {
err = -EINVAL;
goto out;
}
err = copy_to_user((void __user *)buf, init_ents,
array_size(entries, cqe_size)) ?
copy_bytes) ?
-EFAULT : 0;
}