From 80eaf453c279bc82abe0e32e5eb663be0e3cb265 Mon Sep 17 00:00:00 2001 From: David Gibson Date: Mon, 9 Jul 2018 14:50:38 +1000 Subject: libfdt: Add necessary header padding in fdt_create() At present fdt_create() will succeed if there is exactly enough space to put in the fdt header. However, it sets the off_mem_rsvmap field, a few bytes past that in order to align the memory reservation block. Having block pointers pointing past the end of the fdt is pretty ugly, even if it is just a transient state. Worse, if fdt_resize() is called at exactly the wrong time, it can end up accessing data past the blob's allocated space because of this. So, correct fdt_create() to ensure that there is sufficient space for the alignment padding as well as the plain header. For paranoia, also add a check in fdt_resize() to make sure we don't copy data from outside the blob's bounds. Signed-off-by: David Gibson --- cpukit/dtc/libfdt/fdt_sw.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/cpukit/dtc/libfdt/fdt_sw.c b/cpukit/dtc/libfdt/fdt_sw.c index 024f4d85de..9fa4a94d83 100644 --- a/cpukit/dtc/libfdt/fdt_sw.c +++ b/cpukit/dtc/libfdt/fdt_sw.c @@ -143,9 +143,11 @@ static void *fdt_grab_space_(void *fdt, size_t len) int fdt_create(void *buf, int bufsize) { + const size_t hdrsize = FDT_ALIGN(sizeof(struct fdt_header), + sizeof(struct fdt_reserve_entry)); void *fdt = buf; - if (bufsize < sizeof(struct fdt_header)) + if (bufsize < hdrsize) return -FDT_ERR_NOSPACE; memset(buf, 0, bufsize); @@ -155,8 +157,7 @@ int fdt_create(void *buf, int bufsize) fdt_set_last_comp_version(fdt, FDT_FIRST_SUPPORTED_VERSION); fdt_set_totalsize(fdt, bufsize); - fdt_set_off_mem_rsvmap(fdt, FDT_ALIGN(sizeof(struct fdt_header), - sizeof(struct fdt_reserve_entry))); + fdt_set_off_mem_rsvmap(fdt, hdrsize); fdt_set_off_dt_struct(fdt, fdt_off_mem_rsvmap(fdt)); fdt_set_off_dt_strings(fdt, 0); @@ -173,6 +174,9 @@ int fdt_resize(void *fdt, void *buf, int bufsize) headsize = fdt_off_dt_struct(fdt) + fdt_size_dt_struct(fdt); tailsize = fdt_size_dt_strings(fdt); + if ((headsize + tailsize) > fdt_totalsize(fdt)) + return -FDT_ERR_INTERNAL; + if ((headsize + tailsize) > bufsize) return -FDT_ERR_NOSPACE; -- cgit v1.2.3