See fs/xattr.c::xattr_permission()"
/*
* In the user.* namespace, only regular files and directories can have
* extended attributes. For sticky directories, only the owner and
* privileged users can write attributes.
*/
if (!strncmp(name, XATTR_USER_PREFIX, XATTR_USER_PREFIX_LEN)) {
if (!S_ISREG(inode->i_mode) && !S_ISDIR(inode->i_mode))
return (mask & MAY_WRITE) ? -EPERM : -ENODATA;
if (S_ISDIR(inode->i_mode) && (inode->i_mode & S_ISVTX) &&
(mask & MAY_WRITE) && !inode_owner_or_capable(inode))
return -EPERM;
}
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
If the file descriptors received in SCM_RIGHTS would cause
the process to its exceed RLIMIT_NOFILE limit, the excess
FDs are discarded.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Long ago, the sysvipc.7 page was called ipc.5, which was both a
misnaming (too general a name) and an inconsistent section. The
page was renamed (to svipc.7) many years ago, and the link with
the old name has probably ceased to be needed. So, remove it.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Here's a program for doing experiments:
/* on_expt_scope_expt.c
(C) Michael Kerrisk, 2019, Licensed GNU GPLv2+
*/
char *tos;
static void
exitFunc(int status, void *p)
{
int efloc;
int *xp = (int *) p;
printf("====== Entered exit handler\n");
printf("&efloc = %p (0x%llx)\n",
(void *) &efloc, (long long) (tos - (char *) &efloc));
printf("xp = %p (value: %d)\n", (void *) xp, *xp);
if (*xp != INIT_VALUE)
printf("It looks like the variable passed to the exit handler "
"has gone out of scope\n");
/* Produce a core dump, which we can examine with GDB to look at the
frames on the stack, if desired */
printf("===\n");
printf("About to abort\n");
abort();
}
static void
recur(int lev, int *xp)
{
int rloc;
int big[65536-12]; /* 12*4 == 48 other bytes allocated on
this stack frame */
tos = (char *) &rloc;
big[0] = lev;
big[0]++;
printf("&rloc = %p (%d) (%d)\n", (void *) &rloc, lev, *xp);
if (lev > 1)
recur(lev - 1, xp);
else {
printf("exit() from recur()\n");
exit(EXIT_SUCCESS);
}
}
int
main(int argc, char *argv[])
{
int lev;
int *xp;
int xx;
if (argc < 2) {
fprintf(stderr, "Usage: %s {s|h} [how]\n", argv[0]);
fprintf(stderr, "\ts => exitFunc() arg is in main() stack\n");
fprintf(stderr, "\th => exitFunc() arg is allocated on heapn");
fprintf(stderr, "\tIf 'how' is not present, then return from main()\n");
fprintf(stderr, "\tIf 'how' is 0, then exit() from main()\n");
fprintf(stderr, "\tIf 'how' is > 0, then make 'how' recursive "
"function calls, and then exit()\n");
exit(EXIT_FAILURE);
}
tos = (char *) &xp;
if (argv[1][0] == 'h') {
xp = malloc(sizeof(int));
if (xp == NULL) {
perror("malloc");
exit(EXIT_FAILURE);
}
printf("Argument for exitFunc() is allocated on heap\n");
} else {
xp = &xx;
printf("Argument for exitFunc() is allocated on stack in main()\n");
}
*xp = INIT_VALUE;
printf("xp = %p (value: %d)\n", (void *) xp, *xp);
printf("===\n");
on_exit(exitFunc, xp);
if (argc == 2) {
printf("return from main\n");
return 0;
}
lev = atoi(argv[2]);
if (lev < 1) {
printf("Calling exit() from main\n");
exit(EXIT_SUCCESS);
} else {
recur(lev, xp);
}
}
Reported-by: Sami Kerola <kerolasa@iki.fi>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
To get the pkey_alloc, pkey_free and pkey_mprotect functions
_GNU_SOURCE needs to be defined before including sys/mman.h.
Reviewed-by: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Mark Wielaard <mark@klomp.org>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The mprotect.2 NOTES say:
On systems that do not support protection keys in
hardware, pkey_mprotect() may still be used, but pkey must
be set to 0. When called this way, the operation of
pkey_mprotect() is equivalent to mprotect().
But this is not what the glibc manual says:
It is also possible to call pkey_mprotect with a key value
of -1, in which case it will behave in the same way as
mprotect.
Which is correct. Both the glibc implementation and the
kernel check whether pkey is -1. 0 is not a valid pkey when
memory protection keys are not supported in hardware.
Signed-off-by: Mark Wielaard <mark@klomp.org>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
I've found the exec man page quite difficult to read when trying
to find the behavior for a specific function. Since the names of
the functions are inline and the order of the descriptions isn't
clear, it's hard to find which paragraphs apply to each function.
I thought it would be much easier to read if the grouping based on
letters is stated.
The Blackfin port was removed in Linux 4.17. Mention this in the
section concerning Blackfin vDSO functions.
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Improved the readability of a sentence that describes the use of
FAN_REPORT_FID and how this particular flag influences what data
structures a listening application could expect to receive when
describing an event.
Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Document the symbols exported by the RISCV vDSO which is present
from kernel 4.15 onwards.
See kernel source files in arch/riscv/kernel/vdso.
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Reviewed-by: Palmer Dabbelt <palmer@sifive.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Details relating to the new initialization flag FAN_REPORT_FID has been
added. As part of the FAN_REPORT_FID feature, a new set of event masks are
available and have been documented accordingly.
A simple example program has been added to also support the understanding
and use of FAN_REPORT_FID and directory modification events.
Signed-off-by: Matthew Bobrowski <mbobrowski@mbobrowski.org>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Michael Kerrisk