From: Max Filippov jcmvbkbc@gmail.com
commit 2217b982624680d19a80ebb4600d05c8586c4f96 upstream.
binfmt_flat loader uses the gap between text and data to store data segment pointers for the libraries. Even in the absence of shared libraries it stores at least one pointer to the executable's own data segment. Text and data can go back to back in the flat binary image and without offsetting data segment last few instructions in the text segment may get corrupted by the data segment pointer.
Fix it by reverting commit a2357223c50a ("binfmt_flat: don't offset the data start").
Cc: stable@vger.kernel.org Fixes: a2357223c50a ("binfmt_flat: don't offset the data start") Signed-off-by: Max Filippov jcmvbkbc@gmail.com Signed-off-by: Greg Ungerer gerg@linux-m68k.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/binfmt_flat.c | 20 ++++++++++++-------- 1 file changed, 12 insertions(+), 8 deletions(-)
--- a/fs/binfmt_flat.c +++ b/fs/binfmt_flat.c @@ -571,7 +571,7 @@ static int load_flat_file(struct linux_b goto err; }
- len = data_len + extra; + len = data_len + extra + MAX_SHARED_LIBS * sizeof(unsigned long); len = PAGE_ALIGN(len); realdatastart = vm_mmap(NULL, 0, len, PROT_READ|PROT_WRITE|PROT_EXEC, MAP_PRIVATE, 0); @@ -585,7 +585,9 @@ static int load_flat_file(struct linux_b vm_munmap(textpos, text_len); goto err; } - datapos = ALIGN(realdatastart, FLAT_DATA_ALIGN); + datapos = ALIGN(realdatastart + + MAX_SHARED_LIBS * sizeof(unsigned long), + FLAT_DATA_ALIGN);
pr_debug("Allocated data+bss+stack (%u bytes): %lx\n", data_len + bss_len + stack_len, datapos); @@ -615,7 +617,7 @@ static int load_flat_file(struct linux_b memp_size = len; } else {
- len = text_len + data_len + extra; + len = text_len + data_len + extra + MAX_SHARED_LIBS * sizeof(u32); len = PAGE_ALIGN(len); textpos = vm_mmap(NULL, 0, len, PROT_READ | PROT_EXEC | PROT_WRITE, MAP_PRIVATE, 0); @@ -630,7 +632,9 @@ static int load_flat_file(struct linux_b }
realdatastart = textpos + ntohl(hdr->data_start); - datapos = ALIGN(realdatastart, FLAT_DATA_ALIGN); + datapos = ALIGN(realdatastart + + MAX_SHARED_LIBS * sizeof(u32), + FLAT_DATA_ALIGN);
reloc = (__be32 __user *) (datapos + (ntohl(hdr->reloc_start) - text_len)); @@ -647,9 +651,8 @@ static int load_flat_file(struct linux_b (text_len + full_data - sizeof(struct flat_hdr)), 0); - if (datapos != realdatastart) - memmove((void *)datapos, (void *)realdatastart, - full_data); + memmove((void *) datapos, (void *) realdatastart, + full_data); #else /* * This is used on MMU systems mainly for testing. @@ -705,7 +708,8 @@ static int load_flat_file(struct linux_b if (IS_ERR_VALUE(result)) { ret = result; pr_err("Unable to read code+data+bss, errno %d\n", ret); - vm_munmap(textpos, text_len + data_len + extra); + vm_munmap(textpos, text_len + data_len + extra + + MAX_SHARED_LIBS * sizeof(u32)); goto err; } }