CVE-2021-47541

In the Linux kernel, the following vulnerability has been resolved:

net/mlx4_en: Fix an use-after-free bug in mlx4_en_try_alloc_resources()

In mlx4_en_try_alloc_resources(), mlx4_en_copy_priv() is called and

tmp->tx_cq will be freed on the error path of mlx4_en_copy_priv().

After that mlx4_en_alloc_resources() is called and there is a dereference

of &tmp->tx_cq[t][i] in mlx4_en_alloc_resources(), which could lead to

a use after free problem on failure of mlx4_en_copy_priv().

Fix this bug by adding a check of mlx4_en_copy_priv()

This bug was found by a static analyzer. The analysis employs

differential checking to identify inconsistent security operations

(e.g., checks or kfrees) between two code paths and confirms that the

inconsistent operations are not recovered in the current function or

the callers, so they constitute bugs.

Note that, as a bug found by static analysis, it can be a false

positive or hard to trigger. Multiple researchers have cross-reviewed

the bug.

Builds with CONFIG_MLX4_EN=m show no new warnings,

and our static analyzer no longer warns about this code.