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vcs-svn: guard against overflow when computing preimage length

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Signed integer overflow produces undefined behavior in C and off_t is
a signed type.  For predictable behavior, add some checks to protect
in advance against overflow.

On 32-bit systems ftell as called by buffer_tmpfile_prepare_to_read
is likely to fail with EOVERFLOW when reading the corresponding
postimage, and this patch does not fix that.  So it's more of a
futureproofing measure than a complete fix.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
This commit is contained in:
Jonathan Nieder 2011-05-27 05:18:33 -05:00
parent 157415a9a9
commit abe27c0cbd
1 changed files with 14 additions and 1 deletions
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15
vcs-svn/fast_export.c
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@ -166,6 +166,7 @@ static int ends_with(const char *s, size_t len, const char *suffix)
static int parse_cat_response_line(const char *header, off_t *len)
{
size_t headerlen = strlen(header);
uintmax_t n;
const char *type;
const char *end;
@ -174,14 +175,25 @@ static int parse_cat_response_line(const char *header, off_t *len)
type = memmem(header, headerlen, " blob ", strlen(" blob "));
if (!type)
return error("cat-blob header has wrong object type: %s", header);
*len = strtoumax(type + strlen(" blob "), (char **) &end, 10);
n = strtoumax(type + strlen(" blob "), (char **) &end, 10);
if (end == type + strlen(" blob "))
return error("cat-blob header does not contain length: %s", header);
if (memchr(type + strlen(" blob "), '-', end - type - strlen(" blob ")))
return error("cat-blob header contains negative length: %s", header);
if (n == UINTMAX_MAX || n > maximum_signed_value_of_type(off_t))
return error("blob too large for current definition of off_t");
*len = n;
if (*end)
return error("cat-blob header contains garbage after length: %s", header);
return 0;
}
static void check_preimage_overflow(off_t a, off_t b)
{
if (signed_add_overflows(a, b))
die("blob too large for current definition of off_t");
}
static long apply_delta(off_t len, struct line_buffer *input,
const char *old_data, uint32_t old_mode)
{
@ -204,6 +216,7 @@ static long apply_delta(off_t len, struct line_buffer *input,
}
if (old_mode == REPO_MODE_LNK) {
strbuf_addstr(&preimage.buf, "link ");
check_preimage_overflow(preimage_len, strlen("link "));
preimage_len += strlen("link ");
}
if (svndiff0_apply(input, len, &preimage, out))