The struct shmdir_name in include/shm-directory.h has name field to
contains the full path of the POSIX IPC object (shm and sem).
The size was previously set to sizeof (SHMDIR) + 4 + NAME_MAX, where 4
bytes were reserved for the optional "sem." prefix.
This led to incorrect execution of the __shm_get_name function
in posix/shm-directory.c which is used accross in shm_[open/unlink] and
sem_[open/unlink] functions.
For shm_[open/unlink]:
This is because the name field was large enough to hold 268 characters
(255 + 4 + 9) instead of the maximum allowed 263 characters (255 + 9).
This caused the __shm_get_name to not throw ENAMETOOLONG error when the
name length exceeded NAME_MAX (255) upto 259 characters.
For sem_[open/unlink]:
Similarly, the __shm_get_name incorrectly returned success for names of
length 255 instead of 251 (255 - 4).
This was overlooked as finally these functions throw the correct
ENAMETOOLONG error; which was thrown by the openat syscall, which is
called later in the shm_* and sem_* functions.
This patch corrects the size of name field in struct shmdir_name to
sizeof (SHMDIR) + NAME_MAX. The __shm_get_name function return
ENAMETOOLONG if alloc_buffer_has_failed returns true (which only happens
when copy length > alloc_buffer_size (buffer)).
Relevant runtime monitoring were done in gdb to confirm the same.
Signed-off-by: Prasanna Paithankar <paithankarprasanna@gmail.com>
Reviewed-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
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