libio: Check remaining buffer size in _IO_wdo_write (bug 31183)

The multibyte character needs to fit into the remaining buffer space,
not the already-written buffer space.  Without the fix, we were never
moving the write pointer from the start of the buffer, always using
the single-character fallback buffer.

Fixes commit 04b76b5aa8 ("Don't error out writing
a multibyte character to an unbuffered stream (bug 17522)").

(cherry picked from commit ecc7c3deb9)
This commit is contained in:
Florian Weimer 2024-01-02 14:36:17 +01:00
parent 9b90e763db
commit bd9f194c34
2 changed files with 2 additions and 1 deletions

1
NEWS
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@ -55,6 +55,7 @@ The following bugs are resolved with this release:
[30745] Slight bug in cache info codes for x86
[30842] Stack read overflow in getaddrinfo in no-aaaa mode (CVE-2023-4527)
[30843] potential use-after-free in getcanonname (CVE-2023-4806)
[31183] Wide stream buffer size reduced MB_LEN_MAX bytes after bug 17522 fix
[31184] FAIL: elf/tst-tlsgap
[31185] Incorrect thread point access in _dl_tlsdesc_undefweak and _dl_tlsdesc_dynamic

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@ -55,7 +55,7 @@ _IO_wdo_write (FILE *fp, const wchar_t *data, size_t to_do)
char mb_buf[MB_LEN_MAX];
char *write_base, *write_ptr, *buf_end;
if (fp->_IO_write_ptr - fp->_IO_write_base < sizeof (mb_buf))
if (fp->_IO_buf_end - fp->_IO_write_ptr < sizeof (mb_buf))
{
/* Make sure we have room for at least one multibyte
character. */