From cd9aea32cffd8089f6f63f4eb86d4dccfc0b3850 Mon Sep 17 00:00:00 2001 From: Indu Bhagat Date: Fri, 6 Jan 2023 09:29:48 -0800 Subject: [PATCH] libsframe: adjust an incorrect check in flip_sframe When sframe_encoder_write needs to flip the buffer containing the SFrame section before writing, it is not necessary that the SFrame FDES are in the order of their sfde_func_start_fre_off. On the contrary, SFrame FDEs will be sorted in the order of their start address. So, remove this incorrect assumption which is basically assuming that the last sfde_func_start_fre_off seen will help determine the end of the flipped buffer. The function now keeps track of the bytes_flipped and then compares it with the expected value. Also, added two more checks at appropriate places: - check that the SFrame FDE read is within bounds - check that the SFrame FRE read is within bounds libsframe/ * sframe.c (flip_sframe): Adjust an incorrect check. Add other checks to ensure reads are within the buffer size. --- libsframe/sframe.c | 22 +++++++++++++--------- 1 file changed, 13 insertions(+), 9 deletions(-) diff --git a/libsframe/sframe.c b/libsframe/sframe.c index 4aada1a25e0..d206780289a 100644 --- a/libsframe/sframe.c +++ b/libsframe/sframe.c @@ -401,7 +401,10 @@ flip_sframe (char *frame_buf, size_t buf_size, uint32_t to_foreign) unsigned int fre_type = 0; uint32_t fre_offset = 0; size_t esz = 0; + size_t hdrsz = 0; int err = 0; + /* For error checking. */ + size_t bytes_flipped = 0; /* Header must be in host endianness at this time. */ ihp = (sframe_header *)frame_buf; @@ -411,14 +414,18 @@ flip_sframe (char *frame_buf, size_t buf_size, uint32_t to_foreign) /* The contents of the SFrame header are safe to read. Get the number of FDEs and the first FDE in the buffer. */ + hdrsz = sframe_get_hdr_size (ihp); num_fdes = ihp->sfh_num_fdes; - fdes = frame_buf + sframe_get_hdr_size (ihp) + ihp->sfh_fdeoff; + fdes = frame_buf + hdrsz + ihp->sfh_fdeoff; fdep = (sframe_func_desc_entry *)fdes; j = 0; prev_frep_index = 0; for (i = 0; i < num_fdes; fdep++, i++) { + if ((char*)fdep >= (frame_buf + buf_size)) + goto bad; + if (to_foreign) { num_fres = fdep->sfde_func_num_fres; @@ -427,6 +434,7 @@ flip_sframe (char *frame_buf, size_t buf_size, uint32_t to_foreign) } flip_fde (fdep); + bytes_flipped += sizeof (sframe_func_desc_entry); if (!to_foreign) { @@ -441,20 +449,16 @@ flip_sframe (char *frame_buf, size_t buf_size, uint32_t to_foreign) { if (flip_fre (fp, fre_type, &esz)) goto bad; + bytes_flipped += esz; - if (esz == 0) + if (esz == 0 || esz > buf_size) goto bad; fp += esz; } prev_frep_index = j; } - /* All FREs must have been endian flipped by now. */ - if (j != ihp->sfh_num_fres) - goto bad; - /* Contents, if any, must have been processed by now. - Recall that .sframe section with just a SFrame header may be generated by - GAS if no SFrame FDEs were found for the input file. */ - if (ihp->sfh_num_fres && ((frame_buf + buf_size) != (void*)fp)) + /* All FDEs and FREs must have been endian flipped by now. */ + if ((j != ihp->sfh_num_fres) || (bytes_flipped != (buf_size - hdrsz))) goto bad; /* Success. */ -- 2.30.2