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Subject[PATCH 4/7] pstore/ram_core: Better ECC size checking
Date
- Instead of exploiting unsigned overflows (which doesn't work for all
sizes), use straightforward checking for ECC total size not exceeding
initial buffer size;

- Printing overflowed buffer_size is not informative. Instead, print
ecc_size and buffer_size;

- No need for buffer_size argument in persistent_ram_init_ecc(),
we can address prz->buffer_size directly.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
---
fs/pstore/ram_core.c | 16 ++++++++--------
1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/fs/pstore/ram_core.c b/fs/pstore/ram_core.c
index f62ebf2..a5a7b13 100644
--- a/fs/pstore/ram_core.c
+++ b/fs/pstore/ram_core.c
@@ -171,12 +171,12 @@ static void persistent_ram_ecc_old(struct persistent_ram_zone *prz)
}
}

-static int persistent_ram_init_ecc(struct persistent_ram_zone *prz,
- size_t buffer_size)
+static int persistent_ram_init_ecc(struct persistent_ram_zone *prz)
{
int numerr;
struct persistent_ram_buffer *buffer = prz->buffer;
int ecc_blocks;
+ size_t ecc_total;

if (!prz->ecc)
return 0;
@@ -187,14 +187,14 @@ static int persistent_ram_init_ecc(struct persistent_ram_zone *prz,
prz->ecc_poly = 0x11d;

ecc_blocks = DIV_ROUND_UP(prz->buffer_size, prz->ecc_block_size);
- prz->buffer_size -= (ecc_blocks + 1) * prz->ecc_size;
-
- if (prz->buffer_size > buffer_size) {
- pr_err("persistent_ram: invalid size %zu, non-ecc datasize %zu\n",
- buffer_size, prz->buffer_size);
+ ecc_total = (ecc_blocks + 1) * prz->ecc_size;
+ if (ecc_total >= prz->buffer_size) {
+ pr_err("%s: invalid ecc_size %u (total %zu, buffer size %zu)\n",
+ __func__, prz->ecc_size, ecc_total, prz->buffer_size);
return -EINVAL;
}

+ prz->buffer_size -= ecc_total;
prz->par_buffer = buffer->data + prz->buffer_size;
prz->par_header = prz->par_buffer + ecc_blocks * prz->ecc_size;

@@ -397,7 +397,7 @@ static int __devinit persistent_ram_post_init(struct persistent_ram_zone *prz,

prz->ecc = ecc;

- ret = persistent_ram_init_ecc(prz, prz->buffer_size);
+ ret = persistent_ram_init_ecc(prz);
if (ret)
return ret;

--
1.7.10.4


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