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Subject[PATCH -next] pstore/ram: Do not use stack VLA for parity workspace
Instead of using a stack VLA for the parity workspace, preallocate a
memory region. The preallocation is done to keep from needing to perform
allocations during crash dump writing, etc. This also fixes a missed
release of librs on free.

Signed-off-by: Kees Cook <keescook@chromium.org>
---
fs/pstore/ram_core.c | 29 ++++++++++++++++++++++-------
include/linux/pstore_ram.h | 1 +
2 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
index e11672aa4575..951a14edcf51 100644
--- a/fs/pstore/ram_core.c
+++ b/fs/pstore/ram_core.c
@@ -98,24 +98,23 @@ static void notrace persistent_ram_encode_rs8(struct persistent_ram_zone *prz,
uint8_t *data, size_t len, uint8_t *ecc)
{
int i;
- uint16_t par[prz->ecc_info.ecc_size];

/* Initialize the parity buffer */
- memset(par, 0, sizeof(par));
- encode_rs8(prz->rs_decoder, data, len, par, 0);
+ memset(prz->ecc_info.par, 0,
+ prz->ecc_info.ecc_size * sizeof(prz->ecc_info.par[0]));
+ encode_rs8(prz->rs_decoder, data, len, prz->ecc_info.par, 0);
for (i = 0; i < prz->ecc_info.ecc_size; i++)
- ecc[i] = par[i];
+ ecc[i] = prz->ecc_info.par[i];
}

static int persistent_ram_decode_rs8(struct persistent_ram_zone *prz,
void *data, size_t len, uint8_t *ecc)
{
int i;
- uint16_t par[prz->ecc_info.ecc_size];

for (i = 0; i < prz->ecc_info.ecc_size; i++)
- par[i] = ecc[i];
- return decode_rs8(prz->rs_decoder, data, par, len,
+ prz->ecc_info.par[i] = ecc[i];
+ return decode_rs8(prz->rs_decoder, data, prz->ecc_info.par, len,
NULL, 0, NULL, 0, NULL);
}

@@ -228,6 +227,15 @@ static int persistent_ram_init_ecc(struct persistent_ram_zone *prz,
return -EINVAL;
}

+ /* allocate workspace instead of using stack VLA */
+ prz->ecc_info.par = kmalloc_array(prz->ecc_info.ecc_size,
+ sizeof(*prz->ecc_info.par),
+ GFP_KERNEL);
+ if (!prz->ecc_info.par) {
+ pr_err("cannot allocate ECC parity workspace\n");
+ return -ENOMEM;
+ }
+
prz->corrected_bytes = 0;
prz->bad_blocks = 0;

@@ -514,6 +522,13 @@ void persistent_ram_free(struct persistent_ram_zone *prz)
}
prz->vaddr = NULL;
}
+ if (prz->rs_decoder) {
+ free_rs(prz->rs_decoder);
+ prz->rs_decoder = NULL;
+ }
+ kfree(prz->ecc_info.par);
+ prz->ecc_info.par = NULL;
+
persistent_ram_free_old(prz);
kfree(prz);
}
diff --git a/include/linux/pstore_ram.h b/include/linux/pstore_ram.h
index 9395f06e8372..e6d226464838 100644
--- a/include/linux/pstore_ram.h
+++ b/include/linux/pstore_ram.h
@@ -39,6 +39,7 @@ struct persistent_ram_ecc_info {
int ecc_size;
int symsize;
int poly;
+ uint16_t *par;
};

struct persistent_ram_zone {
--
2.7.4

--
Kees Cook
Pixel Security

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