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firmware: improve LSM/IMA security behaviour 

The firmware loader queries if LSM/IMA permits it to load firmware
via the sysfs fallback. Unfortunately, the code does the opposite:
it expressly permits sysfs fw loading if security_kernel_load_data(
LOADING_FIRMWARE) returns -EACCES. This happens because a
zero-on-success return value is cast to a bool that's true on success.

Fix the return value handling so we get the correct behaviour.

Fixes: 6e852651f2 ("firmware: add call to LSM hook before firmware sysfs fallback")
Cc: Stable <stable@vger.kernel.org>
Cc: Mimi Zohar <zohar@linux.vnet.ibm.com>
Cc: Kees Cook <keescook@chromium.org>
To: Luis Chamberlain <mcgrof@kernel.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Sven Van Asbroeck <TheSven73@gmail.com>
Reviewed-by: Mimi Zohar <zohar@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Sven Van Asbroeck 2019-06-17 14:23:54 -04:00 committed by Greg Kroah-Hartman
parent 5669245b57
commit 2472d64af2
1 changed files with 1 additions and 1 deletions
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2
drivers/base/firmware_loader/fallback.c
View File

@ -659,7 +659,7 @@ static bool fw_run_sysfs_fallback(enum fw_opt opt_flags)
/* Also permit LSMs and IMA to fail firmware sysfs fallback */ /* Also permit LSMs and IMA to fail firmware sysfs fallback */
ret = security_kernel_load_data(LOADING_FIRMWARE); ret = security_kernel_load_data(LOADING_FIRMWARE);
if (ret < 0) if (ret < 0)
return ret; return false;
return fw_force_sysfs_fallback(opt_flags); return fw_force_sysfs_fallback(opt_flags);
} }