This fixes CVE-2018-18440 ("insufficient boundary checks in filesystem image load") by using lmb to check the load size of a file against reserved memory addresses.
Signed-off-by: Simon Goldschmidt simon.k.r.goldschmidt@gmail.com ---
Changes in v4: None Changes in v2: None
fs/fs.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++++--- include/lmb.h | 2 ++ lib/lmb.c | 13 ++++++++++++ 3 files changed, 68 insertions(+), 3 deletions(-)
diff --git a/fs/fs.c b/fs/fs.c index adae98d021..4baf6b1c39 100644 --- a/fs/fs.c +++ b/fs/fs.c @@ -428,13 +428,57 @@ int fs_size(const char *filename, loff_t *size) return ret; }
-int fs_read(const char *filename, ulong addr, loff_t offset, loff_t len, - loff_t *actread) +#ifdef CONFIG_LMB +/* Check if a file may be read to the given address */ +static int fs_read_lmb_check(const char *filename, ulong addr, loff_t offset, + loff_t len, struct fstype_info *info) +{ + struct lmb lmb; + int ret; + loff_t size; + loff_t read_len; + + /* get the actual size of the file */ + ret = info->size(filename, &size); + if (ret) + return ret; + if (offset >= size) { + /* offset >= EOF, no bytes will be written */ + return 0; + } + read_len = size - offset; + + /* limit to 'len' if it is smaller */ + if (len && len < read_len) + read_len = len; + + lmb_init_and_reserve(&lmb, gd->bd->bi_dram[0].start, + gd->bd->bi_dram[0].size, (void *)gd->fdt_blob); + lmb_dump_all(&lmb); + + if (lmb_alloc_addr(&lmb, addr, read_len) == addr) + return 0; + + printf("** Reading file would overwrite reserved memory **\n"); + return -1; +} +#endif + +static int _fs_read(const char *filename, ulong addr, loff_t offset, loff_t len, + int do_lmb_check, loff_t *actread) { struct fstype_info *info = fs_get_info(fs_type); void *buf; int ret;
+#ifdef CONFIG_LMB + if (do_lmb_check) { + ret = fs_read_lmb_check(filename, addr, offset, len, info); + if (ret) + return ret; + } +#endif + /* * We don't actually know how many bytes are being read, since len==0 * means read the whole file. @@ -451,6 +495,12 @@ int fs_read(const char *filename, ulong addr, loff_t offset, loff_t len, return ret; }
+int fs_read(const char *filename, ulong addr, loff_t offset, loff_t len, + loff_t *actread) +{ + return _fs_read(filename, addr, offset, len, 0, actread); +} + int fs_write(const char *filename, ulong addr, loff_t offset, loff_t len, loff_t *actwrite) { @@ -621,7 +671,7 @@ int do_load(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[], pos = 0;
time = get_timer(0); - ret = fs_read(filename, addr, pos, bytes, &len_read); + ret = _fs_read(filename, addr, pos, bytes, 1, &len_read); time = get_timer(time); if (ret < 0) return 1; diff --git a/include/lmb.h b/include/lmb.h index 7d7e2a78dc..62da85e716 100644 --- a/include/lmb.h +++ b/include/lmb.h @@ -31,6 +31,8 @@ struct lmb { extern struct lmb lmb;
extern void lmb_init(struct lmb *lmb); +extern void lmb_init_and_reserve(struct lmb *lmb, phys_addr_t base, + phys_size_t size, void *fdt_blob); extern long lmb_add(struct lmb *lmb, phys_addr_t base, phys_size_t size); extern long lmb_reserve(struct lmb *lmb, phys_addr_t base, phys_size_t size); extern phys_addr_t lmb_alloc(struct lmb *lmb, phys_size_t size, ulong align); diff --git a/lib/lmb.c b/lib/lmb.c index 9de1581972..776aa7a8b7 100644 --- a/lib/lmb.c +++ b/lib/lmb.c @@ -104,6 +104,19 @@ void lmb_init(struct lmb *lmb) lmb->reserved.size = 0; }
+/* Initialize the struct, add memory and call arch/board reserve functions */ +void lmb_init_and_reserve(struct lmb *lmb, phys_addr_t base, phys_size_t size, + void *fdt_blob) +{ + lmb_init(lmb); + lmb_add(lmb, base, size); + arch_lmb_reserve(lmb); + board_lmb_reserve(lmb); + + if (IMAGE_ENABLE_OF_LIBFDT) + boot_fdt_add_mem_rsv_regions(lmb, fdt_blob); +} + /* This routine called with relocation disabled. */ static long lmb_add_region(struct lmb_region *rgn, phys_addr_t base, phys_size_t size) {