From: Kees Cook <keescook@chromium.org>
To: linux-kernel@vger.kernel.org
Cc: Kees Cook <keescook@chromium.org>,
Joel Fernandes <joel@joelfernandes.org>,
Anton Vorontsov <anton@enomsg.org>,
Colin Cross <ccross@android.com>, Tony Luck <tony.luck@intel.com>
Subject: [PATCH 2/8] pstore: Do not use crash buffer for decompression
Date: Thu, 1 Nov 2018 16:51:54 -0700 [thread overview]
Message-ID: <20181101235200.28584-3-keescook@chromium.org> (raw)
In-Reply-To: <20181101235200.28584-1-keescook@chromium.org>
The pre-allocated compression buffer used for crash dumping was also
being used for decompression. This isn't technically safe, since it's
possible the kernel may attempt a crashdump while pstore is populating the
pstore filesystem (and performing decompression). Instead, just allocate
a separate buffer for decompression. Correctness is preferred over
performance here.
Signed-off-by: Kees Cook <keescook@chromium.org>
---
fs/pstore/platform.c | 56 ++++++++++++++++++++------------------------
1 file changed, 25 insertions(+), 31 deletions(-)
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index b821054ca3ed..8b6028948cf3 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -258,20 +258,6 @@ static int pstore_compress(const void *in, void *out,
return outlen;
}
-static int pstore_decompress(void *in, void *out,
- unsigned int inlen, unsigned int outlen)
-{
- int ret;
-
- ret = crypto_comp_decompress(tfm, in, inlen, out, &outlen);
- if (ret) {
- pr_err("crypto_comp_decompress failed, ret = %d!\n", ret);
- return ret;
- }
-
- return outlen;
-}
-
static void allocate_buf_for_compression(void)
{
struct crypto_comp *ctx;
@@ -656,8 +642,9 @@ EXPORT_SYMBOL_GPL(pstore_unregister);
static void decompress_record(struct pstore_record *record)
{
+ int ret;
int unzipped_len;
- char *decompressed;
+ char *unzipped, *workspace;
if (!record->compressed)
return;
@@ -668,35 +655,42 @@ static void decompress_record(struct pstore_record *record)
return;
}
- /* No compression method has created the common buffer. */
+ /* Missing compression buffer means compression was not initialized. */
if (!big_oops_buf) {
- pr_warn("no decompression buffer allocated\n");
+ pr_warn("no decompression method initialized!\n");
return;
}
- unzipped_len = pstore_decompress(record->buf, big_oops_buf,
- record->size, big_oops_buf_sz);
- if (unzipped_len <= 0) {
- pr_err("decompression failed: %d\n", unzipped_len);
+ /* Allocate enough space to hold max decompression and ECC. */
+ unzipped_len = big_oops_buf_sz;
+ workspace = kmalloc(unzipped_len + record->ecc_notice_size,
+ GFP_KERNEL);
+ if (!workspace)
return;
- }
- /* Build new buffer for decompressed contents. */
- decompressed = kmalloc(unzipped_len + record->ecc_notice_size,
- GFP_KERNEL);
- if (!decompressed) {
- pr_err("decompression ran out of memory\n");
+ /* After decompression "unzipped_len" is almost certainly smaller. */
+ ret = crypto_comp_decompress(tfm, record->buf, record->size,
+ workspace, &unzipped_len);
+ if (ret) {
+ pr_err("crypto_comp_decompress failed, ret = %d!\n", ret);
+ kfree(workspace);
return;
}
- memcpy(decompressed, big_oops_buf, unzipped_len);
/* Append ECC notice to decompressed buffer. */
- memcpy(decompressed + unzipped_len, record->buf + record->size,
+ memcpy(workspace + unzipped_len, record->buf + record->size,
record->ecc_notice_size);
- /* Swap out compresed contents with decompressed contents. */
+ /* Copy decompressed contents into an minimum-sized allocation. */
+ unzipped = kmemdup(workspace, unzipped_len + record->ecc_notice_size,
+ GFP_KERNEL);
+ kfree(workspace);
+ if (!unzipped)
+ return;
+
+ /* Swap out compressed contents with decompressed contents. */
kfree(record->buf);
- record->buf = decompressed;
+ record->buf = unzipped;
record->size = unzipped_len;
record->compressed = false;
}
--
2.17.1
next prev parent reply other threads:[~2018-11-01 23:52 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-01 23:51 [PATCH 0/8] pstore improvements (pstore-next) Kees Cook
2018-11-01 23:51 ` [PATCH linux-next 1/8] pstore/ram: Standardize module name in ramoops Kees Cook
2018-11-01 23:51 ` Kees Cook [this message]
2018-11-02 18:24 ` [PATCH 2/8] pstore: Do not use crash buffer for decompression Joel Fernandes
2018-11-14 7:56 ` Kees Cook
2018-11-20 21:43 ` Joel Fernandes
2018-11-29 22:06 ` Kees Cook
2018-11-30 2:26 ` Joel Fernandes
2018-11-01 23:51 ` [PATCH 3/8] pstore/ram: Report backend assignments with finer granularity Kees Cook
2018-11-01 23:51 ` [PATCH 4/8] pstore/ram: Add kern-doc for struct persistent_ram_zone Kees Cook
2018-11-01 23:51 ` [PATCH 5/8] pstore: Improve and update some comments and status output Kees Cook
2018-11-01 23:51 ` [PATCH 6/8] pstore: Replace open-coded << with BIT() Kees Cook
2018-11-01 23:51 ` [PATCH 7/8] pstore: Remove needless lock during console writes Kees Cook
2018-11-02 18:32 ` Joel Fernandes
2018-11-02 20:40 ` Kees Cook
2018-11-02 21:50 ` Joel Fernandes
2018-11-01 23:52 ` [PATCH 8/8] pstore/ram: Correctly calculate usable PRZ bytes Kees Cook
2018-11-02 18:01 ` Joel Fernandes
2018-11-02 20:00 ` Kees Cook
2018-11-05 4:42 ` Joel Fernandes
2018-11-05 17:04 ` Kees Cook
2018-11-06 4:42 ` Joel Fernandes
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