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Fixed the bug which broke both fgets() and gets(): copying data from the FILE buffer failed to bump the destination string pointer. Also added an abort check in order to avoid turning the memcpy() operation into an uninterruptable sequence.

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This commit is contained in:
Olaf Barthel
2023-09-06 13:27:45 +02:00
parent 2cb54d48a9
commit b94937ff38
2 changed files with 96 additions and 39 deletions
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67
library/stdio_fgets.c
View File

@@ -56,14 +56,14 @@ fgets(char *s,int n,FILE *stream)
assert( s != NULL && stream != NULL );
if(__check_abort_enabled)
if (__check_abort_enabled)
__check_abort();
flockfile(stream);
#if defined(CHECK_FOR_NULL_POINTERS)
{
if(s == NULL || stream == NULL)
if (s == NULL || stream == NULL)
{
SHOWMSG("invalid parameters");
@@ -74,7 +74,7 @@ fgets(char *s,int n,FILE *stream)
}
#endif /* CHECK_FOR_NULL_POINTERS */
if(n <= 0)
if (n <= 0)
{
SHOWMSG("no work to be done");
@@ -85,7 +85,7 @@ fgets(char *s,int n,FILE *stream)
/* Take care of the checks and data structure changes that
* need to be handled only once for this stream.
*/
if(__fgetc_check(stream) < 0)
if (__fgetc_check(stream) < 0)
{
result = NULL;
goto out;
@@ -97,34 +97,54 @@ fgets(char *s,int n,FILE *stream)
/* One off for the terminating '\0'. */
n--;
while(n > 0)
assert( 0 <= file->iob_BufferReadBytes );
assert( file->iob_BufferReadBytes <= file->iob_BufferSize );
assert( file->iob_BufferPosition <= file->iob_BufferSize );
while (n > 0)
{
/* If there is data in the buffer, try to copy it directly
into the string buffer. If there is a line feed in the
buffer, too, try to conclude the read operation. */
if(file->iob_BufferPosition < file->iob_BufferReadBytes)
* into the string buffer. If there is a line feed in the
* buffer, too, try to conclude the read operation.
*/
if (file->iob_BufferPosition < file->iob_BufferReadBytes)
{
const unsigned char * buffer = &file->iob_Buffer[file->iob_BufferPosition];
size_t num_bytes_in_buffer;
const unsigned char * lf;
/* Copy only as much data as will fit into the string buffer. */
assert( file->iob_BufferReadBytes >= file->iob_BufferPosition );
num_bytes_in_buffer = file->iob_BufferReadBytes - file->iob_BufferPosition;
if(num_bytes_in_buffer > (size_t)n)
if (num_bytes_in_buffer > (size_t)n)
num_bytes_in_buffer = n;
/* Try to find a line feed character which could conclude
the read operation if the remaining buffer data, including
the line feed character, fit into the string buffer. */
* the read operation if the remaining buffer data, including
* the line feed character, fit into the string buffer.
*/
lf = (unsigned char *)memchr(buffer, '\n', num_bytes_in_buffer);
if(lf != NULL)
{
size_t num_characters_in_line = lf + 1 - buffer;
/* Give the user a chance to abort what could otherwise
* become an uninterrupted series of copying operations.
*/
if (__check_abort_enabled)
__check_abort();
assert( num_characters_in_line <= num_bytes_in_buffer );
/* Copy the remainder of the read buffer into the
string buffer, including the terminating line
feed character. */
* string buffer, including the terminating line
* feed character.
*/
memmove(s, buffer, num_characters_in_line);
s += num_characters_in_line;
assert( file->iob_BufferPosition + num_characters_in_line <= file->iob_BufferSize );
file->iob_BufferPosition += num_characters_in_line;
@@ -135,20 +155,25 @@ fgets(char *s,int n,FILE *stream)
memmove(s, buffer, num_bytes_in_buffer);
s += num_bytes_in_buffer;
assert( file->iob_BufferPosition + num_bytes_in_buffer <= file->iob_BufferSize );
file->iob_BufferPosition += num_bytes_in_buffer;
/* Stop if the string buffer has been filled. */
assert( n >= num_bytes_in_buffer );
n -= num_bytes_in_buffer;
if(n == 0)
if (n == 0)
break;
}
/* Read the next buffered character; this will refill the read
buffer, if necessary. */
* buffer, if necessary.
*/
c = __getc(stream);
if(c == EOF)
if (c == EOF)
{
if(ferror(stream))
if (ferror(stream))
{
/* Just to be on the safe side. */
(*s) = '\0';
@@ -158,8 +183,9 @@ fgets(char *s,int n,FILE *stream)
}
/* Make sure that we return NULL if we really
didn't read anything at all */
if(s == result)
* didn't read anything at all.
*/
if (s == result)
result = NULL;
break;
@@ -167,9 +193,10 @@ fgets(char *s,int n,FILE *stream)
(*s++) = c;
if(c == '\n')
if (c == '\n')
break;
assert( n > 0 );
n--;
}

68
library/stdio_gets.c
View File

@@ -55,14 +55,14 @@ gets(char *s)
assert( s != NULL );
if(__check_abort_enabled)
if (__check_abort_enabled)
__check_abort();
flockfile(stream);
#if defined(CHECK_FOR_NULL_POINTERS)
{
if(s == NULL)
if (s == NULL)
{
SHOWMSG("invalid parameters");
@@ -77,7 +77,7 @@ gets(char *s)
/* Take care of the checks and data structure changes that
* need to be handled only once for this stream.
*/
if(__fgetc_check(stream) < 0)
if (__fgetc_check(stream) < 0)
{
result = NULL;
goto out;
@@ -86,29 +86,54 @@ gets(char *s)
/* So that we can tell error and 'end of file' conditions apart. */
clearerr(stream);
while(TRUE)
assert( 0 <= file->iob_BufferReadBytes );
assert( file->iob_BufferReadBytes <= file->iob_BufferSize );
assert( file->iob_BufferPosition <= file->iob_BufferSize );
while (TRUE)
{
/* If there is data in the buffer, try to copy it directly
into the string buffer. If there is a line feed in the
buffer, too, try to conclude the read operation. */
if(file->iob_BufferPosition < file->iob_BufferReadBytes)
* into the string buffer. If there is a line feed in the
* buffer, too, try to conclude the read operation.
*/
if (file->iob_BufferPosition < file->iob_BufferReadBytes)
{
size_t num_bytes_in_buffer = file->iob_BufferReadBytes - file->iob_BufferPosition;
const unsigned char * buffer = &file->iob_Buffer[file->iob_BufferPosition];
const unsigned char * lf;
assert( file->iob_BufferReadBytes >= file->iob_BufferPosition );
/* Try to find a line feed character which could conclude
the read operation if the remaining buffer data, including
the line feed character, fit into the string buffer. */
* the read operation if the remaining buffer data, including
* the line feed character, fit into the string buffer.
*/
lf = (unsigned char *)memchr(buffer, '\n', num_bytes_in_buffer);
if(lf != NULL)
if (lf != NULL)
{
size_t num_characters_in_line = lf + 1 - buffer;
assert( num_characters_in_line <= num_bytes_in_buffer );
/* Give the user a chance to abort what could otherwise
* become an uninterrupted series of copying operations.
*/
if (__check_abort_enabled)
__check_abort();
/* Copy the remainder of the read buffer into the
string buffer, including the terminating line
feed character. */
memmove(s, buffer, num_characters_in_line);
* string buffer, omitting the terminating line
* feed character. This is the difference between
* gets() and fgets(): fgets() will keep the
* terminating line feed character, but gets()
* will drop it.
*/
assert( num_characters_in_line > 0 );
memmove(s, buffer, num_characters_in_line - 1);
s += num_characters_in_line - 1;
assert( file->iob_BufferPosition + num_characters_in_line <= file->iob_BufferSize );
file->iob_BufferPosition += num_characters_in_line;
@@ -116,16 +141,20 @@ gets(char *s)
break;
}
assert( num_bytes_in_buffer > 0 );
memmove(s, buffer, num_bytes_in_buffer);
s += num_bytes_in_buffer;
assert( file->iob_BufferPosition + num_bytes_in_buffer <= file->iob_BufferSize );
file->iob_BufferPosition += num_bytes_in_buffer;
}
c = __getc(stream);
if(c == EOF)
if (c == EOF)
{
if(ferror(stream))
if (ferror(stream))
{
/* Just to be on the safe side. */
(*s) = '\0';
@@ -135,14 +164,15 @@ gets(char *s)
}
/* Make sure that we return NULL if we really
didn't read anything at all */
if(s == result)
* didn't read anything at all.
*/
if (s == result)
result = NULL;
break;
}
if(c == '\n')
if (c == '\n')
break;
(*s++) = c;