From: Max Filippov <[email protected]>
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: [email protected]
Fixes: a2357223c50a ("binfmt_flat: don't offset the data start")
Signed-off-by: Max Filippov <[email protected]>
Signed-off-by: Greg Ungerer <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
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;
}
}
