forked from luck/tmp_suning_uos_patched
8ece3b3eb5
Userspace libraries, e.g. glibc's dprintf(), perform a SEEK_CUR operation
over any file descriptor requested to make sure the current position isn't
pointing to junk due to previous manipulation of that same fd. And whenever
that fd doesn't have support for such operation, the userspace code expects
-ESPIPE to be returned.
However, when the fd in question references the /dev/kmsg interface, the
current kernel code state returns -EINVAL instead, causing an unexpected
behavior in userspace: in the case of glibc, when -ESPIPE is returned it
gets ignored and the call completes successfully, while returning -EINVAL
forces dprintf to fail without performing any action over that fd:
if (_IO_SEEKOFF (fp, (off64_t)0, _IO_seek_cur, _IOS_INPUT|_IOS_OUTPUT) ==
_IO_pos_BAD && errno != ESPIPE)
return NULL;
With this patch we make sure to return the correct value when SEEK_CUR is
requested over kmsg and also add some kernel doc information to formalize
this behavior.
Link: https://lore.kernel.org/r/20200317103344.574277-1-bmeneg@redhat.com
Cc: linux-kernel@vger.kernel.org
Cc: rostedt@goodmis.org,
Cc: David.Laight@ACULAB.COM
Signed-off-by: Bruno Meneguele <bmeneg@redhat.com>
Acked-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Signed-off-by: Petr Mladek <pmladek@suse.com>
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|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.