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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id x23sm6851493pfc.170.2021.05.02.10.23.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 02 May 2021 10:23:35 -0700 (PDT) From: Kees Cook To: Greg Kroah-Hartman Cc: Kees Cook , Wenwen Wang , "Rafael J. Wysocki" , Len Brown , linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org Subject: [PATCH] Revert "ACPI: custom_method: fix memory leaks" Date: Sun, 2 May 2021 10:23:26 -0700 Message-Id: <20210502172326.2060025-1-keescook@chromium.org> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Patch-Hashes: v=1; h=sha256; g=27f4a3882208c0c7ab311bccbc7938a98215ce1b; i=4pHPPkCLiO0B5jX/lC0oWvEOjAppjon3wDcV95JIlCY=; m=B7t9QWkqpLbwV/hn+i+5AcQpHIFvut5e6PdfyOfbBvo=; p=dnBvSkSfZUmrGRocFe6rzb+j1MQ4jwUfNvP+Dje0+G8= X-Patch-Sig: m=pgp; i=keescook@chromium.org; s=0x0x8972F4DFDC6DC026; b=iQIzBAABCgAdFiEEpcP2jyKd1g9yPm4TiXL039xtwCYFAmCO4A0ACgkQiXL039xtwCbSqBAAlxq 1U9qI6T30iKOG2xGDH6nuqZSQKjgVrY89a0xtu6Cf+Dl0Tw3HvrLsLmIKppF2y8P02kh8Qgb/0wXK napAXAiwy1VvVuSICbEqtK9UGrbO3PDUPo8hLoOOsGckRVlHNjwk4af++Hri0QWu40SIGBo+AuRTT 8d08tNrswsng7ixEzO13C/rJ6iyFVwp4dF2HTc+VnyHyVKtuhtrZ12jwUuAZ5vOi//HeOGJbQ7HUT tA3IucfVq7xuyVpkREICcQuzzb+pUBwJMCm+4v384J4C0LjQk01f7FSWjpLRHot3UaredQDChe8rk 21Nw3fRd41kFMIzNXDqJyDm2Pd6+jS2r3tkj/493qHHPJGbXdE5L8V8Y6bas1LAuAUNPCtTDCfTW8 MBPkzb1Yrv6atCaG9wU4hD0Q/NrsmMtN/SViur7A/sw0sg161+DWGelyxWjxZHZ+0WnlSMeN848Gb 938HJXrAEI9vfk7ROWV5YbKNDT8onhvS413+uJBGx/I74S3WHG4bUNpYZPObNhETd2F3b9q4YHt0r TCh6wZ7jgpqXwNPQMsPhpoA2z0rKjOgP6zBj2Nyhza1Bw5Hgo8E7lSZ1XfuTsHAynEVf/hiHYMTn1 IMg9Otsq7NFqi7XNusFlVHbR4MbeBlFe2mAT+dB9/IEwm1/fg8mrNa1nQSmDGDEs= Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org This reverts commit 03d1571d9513369c17e6848476763ebbd10ec2cb. While /sys/kernel/debug/acpi/custom_method is already a privileged-only API providing proxied arbitrary write access to kernel memory[1][2], with existing race conditions[3] in buffer allocation and use that could lead to memory leaks and use-after-free conditions, the above commit appears to accidentally make the use-after-free conditions even easier to accomplish. ("buf" is a global variable and prior kfree()s would set buf back to NULL.) This entire interface needs to be reworked (if not entirely removed). [1] https://lore.kernel.org/lkml/20110222193250.GA23913@outflux.net/ [2] https://lore.kernel.org/lkml/201906221659.B618D83@keescook/ [3] https://lore.kernel.org/lkml/20170109231323.GA89642@beast/ Cc: Wenwen Wang Signed-off-by: Kees Cook --- drivers/acpi/custom_method.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-) diff --git a/drivers/acpi/custom_method.c b/drivers/acpi/custom_method.c index 7b54dc95d36b..36d95a02cd30 100644 --- a/drivers/acpi/custom_method.c +++ b/drivers/acpi/custom_method.c @@ -53,10 +53,8 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf, if ((*ppos > max_size) || (*ppos + count > max_size) || (*ppos + count < count) || - (count > uncopied_bytes)) { - kfree(buf); + (count > uncopied_bytes)) return -EINVAL; - } if (copy_from_user(buf + (*ppos), user_buf, count)) { kfree(buf); @@ -76,7 +74,6 @@ static ssize_t cm_write(struct file *file, const char __user * user_buf, add_taint(TAINT_OVERRIDDEN_ACPI_TABLE, LOCKDEP_NOW_UNRELIABLE); } - kfree(buf); return count; }