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Message-Id: <20221018020815.2872331-1-keescook@chromium.org>
Date: Mon, 17 Oct 2022 19:08:09 -0700
From: Kees Cook <keescook@...omium.org>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Kees Cook <keescook@...omium.org>, Tony Luck <tony.luck@...el.com>,
"Guilherme G. Piccoli" <gpiccoli@...lia.com>,
Nick Terrell <terrelln@...com>,
linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/5] pstore: Remove worse-case compression size logic
The worst case compression size is always the size of the uncompressed
data itself so avoid perfectly optimizing the oops buffer size. Hugely
simplifies the code.
Cc: Tony Luck <tony.luck@...el.com>
Cc: "Guilherme G. Piccoli" <gpiccoli@...lia.com>
Cc: Nick Terrell <terrelln@...com>
Cc: linux-hardening@...r.kernel.org
Signed-off-by: Kees Cook <keescook@...omium.org>
---
fs/pstore/platform.c | 144 +++----------------------------------------
1 file changed, 9 insertions(+), 135 deletions(-)
diff --git a/fs/pstore/platform.c b/fs/pstore/platform.c
index cbc0b468c1ab..ef0bc3ae161b 100644
--- a/fs/pstore/platform.c
+++ b/fs/pstore/platform.c
@@ -97,11 +97,6 @@ MODULE_PARM_DESC(kmsg_bytes, "amount of kernel log to snapshot (in bytes)");
/* Compression parameters */
static struct crypto_comp *tfm;
-struct pstore_zbackend {
- int (*zbufsize)(size_t size);
- const char *name;
-};
-
static char *big_oops_buf;
static size_t big_oops_buf_sz;
@@ -168,105 +163,6 @@ static bool pstore_cannot_block_path(enum kmsg_dump_reason reason)
}
}
-#if IS_ENABLED(CONFIG_PSTORE_DEFLATE_COMPRESS)
-static int zbufsize_deflate(size_t size)
-{
- size_t cmpr;
-
- switch (size) {
- /* buffer range for efivars */
- case 1000 ... 2000:
- cmpr = 56;
- break;
- case 2001 ... 3000:
- cmpr = 54;
- break;
- case 3001 ... 3999:
- cmpr = 52;
- break;
- /* buffer range for nvram, erst */
- case 4000 ... 10000:
- cmpr = 45;
- break;
- default:
- cmpr = 60;
- break;
- }
-
- return (size * 100) / cmpr;
-}
-#endif
-
-#if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
-static int zbufsize_lzo(size_t size)
-{
- return lzo1x_worst_compress(size);
-}
-#endif
-
-#if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS) || IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
-static int zbufsize_lz4(size_t size)
-{
- return LZ4_compressBound(size);
-}
-#endif
-
-#if IS_ENABLED(CONFIG_PSTORE_842_COMPRESS)
-static int zbufsize_842(size_t size)
-{
- return size;
-}
-#endif
-
-#if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
-static int zbufsize_zstd(size_t size)
-{
- return zstd_compress_bound(size);
-}
-#endif
-
-static const struct pstore_zbackend *zbackend __ro_after_init;
-
-static const struct pstore_zbackend zbackends[] = {
-#if IS_ENABLED(CONFIG_PSTORE_DEFLATE_COMPRESS)
- {
- .zbufsize = zbufsize_deflate,
- .name = "deflate",
- },
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_LZO_COMPRESS)
- {
- .zbufsize = zbufsize_lzo,
- .name = "lzo",
- },
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_LZ4_COMPRESS)
- {
- .zbufsize = zbufsize_lz4,
- .name = "lz4",
- },
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_LZ4HC_COMPRESS)
- {
- .zbufsize = zbufsize_lz4,
- .name = "lz4hc",
- },
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_842_COMPRESS)
- {
- .zbufsize = zbufsize_842,
- .name = "842",
- },
-#endif
-#if IS_ENABLED(CONFIG_PSTORE_ZSTD_COMPRESS)
- {
- .zbufsize = zbufsize_zstd,
- .name = "zstd",
- },
-#endif
- { }
-};
-
static int pstore_compress(const void *in, void *out,
unsigned int inlen, unsigned int outlen)
{
@@ -291,36 +187,31 @@ static void allocate_buf_for_compression(void)
char *buf;
/* Skip if not built-in or compression backend not selected yet. */
- if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !zbackend)
+ if (!IS_ENABLED(CONFIG_PSTORE_COMPRESS) || !compress)
return;
/* Skip if no pstore backend yet or compression init already done. */
if (!psinfo || tfm)
return;
- if (!crypto_has_comp(zbackend->name, 0, 0)) {
- pr_err("Unknown compression: %s\n", zbackend->name);
- return;
- }
-
- size = zbackend->zbufsize(psinfo->bufsize);
- if (size <= 0) {
- pr_err("Invalid compression size for %s: %d\n",
- zbackend->name, size);
+ if (!crypto_has_comp(compress, 0, 0)) {
+ pr_err("Unknown compression: %s\n", compress);
return;
}
+ /* Worst-case compression should never be more than uncompressed. */
+ size = psinfo->bufsize;
buf = kmalloc(size, GFP_KERNEL);
if (!buf) {
pr_err("Failed %d byte compression buffer allocation for: %s\n",
- size, zbackend->name);
+ size, compress);
return;
}
- ctx = crypto_alloc_comp(zbackend->name, 0, 0);
+ ctx = crypto_alloc_comp(compress, 0, 0);
if (IS_ERR_OR_NULL(ctx)) {
kfree(buf);
- pr_err("crypto_alloc_comp('%s') failed: %ld\n", zbackend->name,
+ pr_err("crypto_alloc_comp('%s') failed: %ld\n", compress,
PTR_ERR(ctx));
return;
}
@@ -330,7 +221,7 @@ static void allocate_buf_for_compression(void)
big_oops_buf_sz = size;
big_oops_buf = buf;
- pr_info("Using crash dump compression: %s\n", zbackend->name);
+ pr_info("Using crash dump compression: %s\n", compress);
}
static void free_buf_for_compression(void)
@@ -818,27 +709,10 @@ static void pstore_timefunc(struct timer_list *unused)
pstore_timer_kick();
}
-static void __init pstore_choose_compression(void)
-{
- const struct pstore_zbackend *step;
-
- if (!compress)
- return;
-
- for (step = zbackends; step->name; step++) {
- if (!strcmp(compress, step->name)) {
- zbackend = step;
- return;
- }
- }
-}
-
static int __init pstore_init(void)
{
int ret;
- pstore_choose_compression();
-
/*
* Check if any pstore backends registered earlier but did not
* initialize compression because crypto was not ready. If so,
--
2.34.1
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