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* [Bug stdio/31183] New: Wide stream buffer size reduced MB_LEN_MAX bytes after bug 17522 fix
@ 2023-12-20 15:43 fweimer at redhat dot com
2023-12-20 15:43 ` [Bug stdio/31183] " fweimer at redhat dot com
` (2 more replies)
0 siblings, 3 replies; 4+ messages in thread
From: fweimer at redhat dot com @ 2023-12-20 15:43 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=31183
Bug ID: 31183
Summary: Wide stream buffer size reduced MB_LEN_MAX bytes after
bug 17522 fix
Product: glibc
Version: 2.21
Status: NEW
Severity: normal
Priority: P2
Component: stdio
Assignee: fweimer at redhat dot com
Reporter: fweimer at redhat dot com
Target Milestone: ---
After the fix from bug 17522, we do not use the remaining buffer space if the
already-written buffer space is smaller than MB_LEN_MAX (16 bytes). As we
start out with no written bytes (zero), we never use the full buffer, greatly
reducing performance.
The fix probably explains it better:
- 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. */
write_ptr = write_base = mb_buf;
buf_end = mb_buf + sizeof (mb_buf);
}
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* [Bug stdio/31183] Wide stream buffer size reduced MB_LEN_MAX bytes after bug 17522 fix
2023-12-20 15:43 [Bug stdio/31183] New: Wide stream buffer size reduced MB_LEN_MAX bytes after bug 17522 fix fweimer at redhat dot com
@ 2023-12-20 15:43 ` fweimer at redhat dot com
2023-12-20 16:17 ` fweimer at redhat dot com
2024-01-02 13:43 ` fweimer at redhat dot com
2 siblings, 0 replies; 4+ messages in thread
From: fweimer at redhat dot com @ 2023-12-20 15:43 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=31183
Florian Weimer <fweimer at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|NEW |ASSIGNED
Flags| |security-
CC| |fweimer at redhat dot com
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* [Bug stdio/31183] Wide stream buffer size reduced MB_LEN_MAX bytes after bug 17522 fix
2023-12-20 15:43 [Bug stdio/31183] New: Wide stream buffer size reduced MB_LEN_MAX bytes after bug 17522 fix fweimer at redhat dot com
2023-12-20 15:43 ` [Bug stdio/31183] " fweimer at redhat dot com
@ 2023-12-20 16:17 ` fweimer at redhat dot com
2024-01-02 13:43 ` fweimer at redhat dot com
2 siblings, 0 replies; 4+ messages in thread
From: fweimer at redhat dot com @ 2023-12-20 16:17 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=31183
--- Comment #1 from Florian Weimer <fweimer at redhat dot com> ---
Patch posted:
[PATCH] libio: Check remaining buffer size in _IO_wdo_write (bug 31183)
<https://inbox.sourceware.org/libc-alpha/87bkakx3b0.fsf@oldenburg.str.redhat.com/>
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* [Bug stdio/31183] Wide stream buffer size reduced MB_LEN_MAX bytes after bug 17522 fix
2023-12-20 15:43 [Bug stdio/31183] New: Wide stream buffer size reduced MB_LEN_MAX bytes after bug 17522 fix fweimer at redhat dot com
2023-12-20 15:43 ` [Bug stdio/31183] " fweimer at redhat dot com
2023-12-20 16:17 ` fweimer at redhat dot com
@ 2024-01-02 13:43 ` fweimer at redhat dot com
2 siblings, 0 replies; 4+ messages in thread
From: fweimer at redhat dot com @ 2024-01-02 13:43 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=31183
Florian Weimer <fweimer at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Resolution|--- |FIXED
Status|ASSIGNED |RESOLVED
Target Milestone|--- |2.39
--- Comment #2 from Florian Weimer <fweimer at redhat dot com> ---
Fixed for 2.39 via:
commit ecc7c3deb9f347649c2078fcc0f94d4cedf92d60
Author: Florian Weimer <fweimer@redhat.com>
Date: Tue Jan 2 14:36:17 2024 +0100
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 04b76b5aa8b2d1d19066e42dd1 ("Don't error out writing
a multibyte character to an unbuffered stream (bug 17522)").
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2023-12-20 15:43 [Bug stdio/31183] New: Wide stream buffer size reduced MB_LEN_MAX bytes after bug 17522 fix fweimer at redhat dot com
2023-12-20 15:43 ` [Bug stdio/31183] " fweimer at redhat dot com
2023-12-20 16:17 ` fweimer at redhat dot com
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