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Fix buffer overrun in lfs_cache_zero #11614

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Fix buffer overrun in lfs_cache_zero #11614

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28 changes: 13 additions & 15 deletions features/storage/filesystem/littlefs/littlefs/lfs.c
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Original file line number Diff line number Diff line change
Expand Up @@ -116,10 +116,10 @@ static inline void lfs_cache_drop(lfs_t *lfs, lfs_cache_t *rcache) {
rcache->block = 0xffffffff;
}

static inline void lfs_cache_zero(lfs_t *lfs, lfs_cache_t *pcache) {
static inline void lfs_cache_zero(lfs_cache_t *cache, lfs_size_t cache_size) {
// zero to avoid information leak
memset(pcache->buffer, 0xff, lfs->cfg->prog_size);
pcache->block = 0xffffffff;
memset(cache->buffer, 0xff, cache_size);
cache->block = 0xffffffff;
}

static int lfs_cache_flush(lfs_t *lfs,
Expand All @@ -143,7 +143,7 @@ static int lfs_cache_flush(lfs_t *lfs,
}
}

lfs_cache_zero(lfs, pcache);
lfs_cache_zero(pcache, lfs->cfg->prog_size);
}

return 0;
Expand Down Expand Up @@ -1352,6 +1352,9 @@ int lfs_file_opencfg(lfs_t *lfs, lfs_file_t *file,

// allocate buffer if needed
file->cache.block = 0xffffffff;
lfs_size_t cache_buffer_size = (file->flags & 3) == LFS_O_RDONLY
? lfs->cfg->read_size
: lfs->cfg->prog_size;
if (file->cfg && file->cfg->buffer) {
file->cache.buffer = file->cfg->buffer;
} else if (lfs->cfg->file_buffer) {
Expand All @@ -1360,20 +1363,15 @@ int lfs_file_opencfg(lfs_t *lfs, lfs_file_t *file,
return LFS_ERR_NOMEM;
}
file->cache.buffer = lfs->cfg->file_buffer;
} else if ((file->flags & 3) == LFS_O_RDONLY) {
file->cache.buffer = lfs_malloc(lfs->cfg->read_size);
if (!file->cache.buffer) {
return LFS_ERR_NOMEM;
}
} else {
file->cache.buffer = lfs_malloc(lfs->cfg->prog_size);
file->cache.buffer = lfs_malloc(cache_buffer_size);
if (!file->cache.buffer) {
return LFS_ERR_NOMEM;
}
}

// zero to avoid information leak
lfs_cache_zero(lfs, &file->cache);
lfs_cache_zero(&file->cache, cache_buffer_size);

// add to list of files
file->next = lfs->files;
Expand Down Expand Up @@ -1448,7 +1446,7 @@ static int lfs_file_relocate(lfs_t *lfs, lfs_file_t *file) {
memcpy(file->cache.buffer, lfs->pcache.buffer, lfs->cfg->prog_size);
file->cache.block = lfs->pcache.block;
file->cache.off = lfs->pcache.off;
lfs_cache_zero(lfs, &lfs->pcache);
lfs_cache_zero(&lfs->pcache, lfs->cfg->prog_size);

file->block = nblock;
return 0;
Expand Down Expand Up @@ -1669,7 +1667,7 @@ lfs_ssize_t lfs_file_write(lfs_t *lfs, lfs_file_t *file,
}

// mark cache as dirty since we may have read data into it
lfs_cache_zero(lfs, &file->cache);
lfs_cache_zero(&file->cache, lfs->cfg->prog_size);
}

// extend file with new blocks
Expand Down Expand Up @@ -2055,8 +2053,8 @@ static int lfs_init(lfs_t *lfs, const struct lfs_config *cfg) {
}

// zero to avoid information leaks
lfs_cache_zero(lfs, &lfs->rcache);
lfs_cache_zero(lfs, &lfs->pcache);
lfs_cache_zero(&lfs->rcache, lfs->cfg->read_size);
lfs_cache_zero(&lfs->pcache, lfs->cfg->prog_size);

// setup lookahead, round down to nearest 32-bits
LFS_ASSERT(lfs->cfg->lookahead % 32 == 0);
Expand Down