RE: [PATCH v2] Cleanup: Use a negative number for uninitialized file descriptors

[Atsushi Kumagai <ats-kumagai@wm.jp.nec.com>]

Hello,

>Do not use zero to denote an invalid file descriptor.
>
>First, zero is a valid value, although quite unlikely to be used for
>anything except standard input.
>
>Second, open(2) returns a negative value on failure, so there are
>already checks for a negative value in some places.
>
>The purpose of this patch is not to allow running in an evil environment
>(with closed stdin), but to aid in debugging by using a consistent value
>for uninitialized file descriptors which is also regarded as invalid by
>the kernel. For example, attempts to close a negative FD will fail
>(unlike an attempt to close FD 0).
>
>Changes from v1:
>  - Cleanup file descriptor usage in dwarf_info.c and sadump_info.c

Thanks for your quick response.
This fix isn't necessary but better to do it as you said.

Martin, could you rebase your three patches ?
I've updated the devel branch.


Thanks,
Atsushi Kumagai

>Signed-off-by: Petr Tesarik <ptesarik@suse.com>
>
>---
> dwarf_info.c   |  6 ++++--
> makedumpfile.c | 68 +++++++++++++++++++++++++++++++++-------------------------
> makedumpfile.h |  2 +-
> sadump_info.c  |  3 ++-
> 4 files changed, 46 insertions(+), 33 deletions(-)
>
>diff --git a/dwarf_info.c b/dwarf_info.c
>index 8c491d3..4f9ad12 100644
>--- a/dwarf_info.c
>+++ b/dwarf_info.c
>@@ -53,7 +53,9 @@ struct dwarf_info {
> 	char	src_name[LEN_SRCFILE];	/* OUT */
> 	Dwarf_Off die_offset;		/* OUT */
> };
>-static struct dwarf_info	dwarf_info;
>+static struct dwarf_info	dwarf_info = {
>+	.fd_debuginfo = -1,
>+};
>
>
> /*
>@@ -1595,7 +1597,7 @@ set_dwarf_debuginfo(char *mod_name, char *os_release,
> 	if (dwarf_info.module_name
> 			&& strcmp(dwarf_info.module_name, "vmlinux")
> 			&& strcmp(dwarf_info.module_name, "xen-syms")) {
>-		if (dwarf_info.fd_debuginfo > 0)
>+		if (dwarf_info.fd_debuginfo >= 0)
> 			close(dwarf_info.fd_debuginfo);
> 		if (dwarf_info.name_debuginfo)
> 			free(dwarf_info.name_debuginfo);
>diff --git a/makedumpfile.c b/makedumpfile.c
>index 21784e8..d168dfd 100644
>--- a/makedumpfile.c
>+++ b/makedumpfile.c
>@@ -3730,10 +3730,10 @@ free_for_parallel()
> 		return;
>
> 	for (i = 0; i < info->num_threads; i++) {
>-		if (FD_MEMORY_PARALLEL(i) > 0)
>+		if (FD_MEMORY_PARALLEL(i) >= 0)
> 			close(FD_MEMORY_PARALLEL(i));
>
>-		if (FD_BITMAP_MEMORY_PARALLEL(i) > 0)
>+		if (FD_BITMAP_MEMORY_PARALLEL(i) >= 0)
> 			close(FD_BITMAP_MEMORY_PARALLEL(i));
> 	}
> }
>@@ -4038,13 +4038,13 @@ out:
> void
> initialize_bitmap(struct dump_bitmap *bitmap)
> {
>-	if (info->fd_bitmap) {
>+	if (info->fd_bitmap >= 0) {
> 		bitmap->fd        = info->fd_bitmap;
> 		bitmap->file_name = info->name_bitmap;
> 		bitmap->no_block  = -1;
> 		memset(bitmap->buf, 0, BUFSIZE_BITMAP);
> 	} else {
>-		bitmap->fd        = 0;
>+		bitmap->fd        = -1;
> 		bitmap->file_name = NULL;
> 		bitmap->no_block  = -1;
> 		memset(bitmap->buf, 0, info->bufsize_cyclic);
>@@ -4154,7 +4154,7 @@ set_bitmap_buffer(struct dump_bitmap *bitmap, mdf_pfn_t pfn, int val, struct cyc
> int
> set_bitmap(struct dump_bitmap *bitmap, mdf_pfn_t pfn, int val, struct cycle *cycle)
> {
>-	if (bitmap->fd) {
>+	if (bitmap->fd >= 0) {
> 		return set_bitmap_file(bitmap, pfn, val);
> 	} else {
> 		return set_bitmap_buffer(bitmap, pfn, val, cycle);
>@@ -4170,7 +4170,7 @@ sync_bitmap(struct dump_bitmap *bitmap)
> 	/*
> 	 * The bitmap doesn't have the fd, it's a on-memory bitmap.
> 	 */
>-	if (bitmap->fd == 0)
>+	if (bitmap->fd < 0)
> 		return TRUE;
> 	/*
> 	 * The bitmap buffer is not dirty, and it is not necessary
>@@ -5403,7 +5403,7 @@ create_1st_bitmap_buffer(struct cycle *cycle)
> int
> create_1st_bitmap(struct cycle *cycle)
> {
>-	if (info->bitmap1->fd) {
>+	if (info->bitmap1->fd >= 0) {
> 		return create_1st_bitmap_file();
> 	} else {
> 		return create_1st_bitmap_buffer(cycle);
>@@ -5414,7 +5414,7 @@ static inline int
> is_in_segs(unsigned long long paddr)
> {
> 	if (info->flag_refiltering || info->flag_sadump) {
>-		if (info->bitmap1->fd == 0) {
>+		if (info->bitmap1->fd < 0) {
> 			initialize_1st_bitmap(info->bitmap1);
> 			create_1st_bitmap_file();
> 		}
>@@ -5872,7 +5872,7 @@ copy_bitmap_file(void)
> int
> copy_bitmap(void)
> {
>-	if (info->fd_bitmap) {
>+	if (info->fd_bitmap >= 0) {
> 		return copy_bitmap_file();
> 	} else {
> 		return copy_bitmap_buffer();
>@@ -6313,7 +6313,7 @@ prepare_bitmap1_buffer(void)
> 		return FALSE;
> 	}
>
>-	if (info->fd_bitmap) {
>+	if (info->fd_bitmap >= 0) {
> 		if ((info->bitmap1->buf = (char *)malloc(BUFSIZE_BITMAP)) == NULL) {
> 			ERRMSG("Can't allocate memory for the 1st bitmaps's buffer. %s\n",
> 			       strerror(errno));
>@@ -6352,7 +6352,7 @@ prepare_bitmap2_buffer(void)
> 		       strerror(errno));
> 		return FALSE;
> 	}
>-	if (info->fd_bitmap) {
>+	if (info->fd_bitmap >= 0) {
> 		if ((info->bitmap2->buf = (char *)malloc(BUFSIZE_BITMAP)) == NULL) {
> 			ERRMSG("Can't allocate memory for the 2nd bitmaps's buffer. %s\n",
> 			       strerror(errno));
>@@ -7582,7 +7582,7 @@ kdump_thread_function_cyclic(void *arg) {
>
> 	fd_memory = FD_MEMORY_PARALLEL(kdump_thread_args->thread_num);
>
>-	if (info->fd_bitmap) {
>+	if (info->fd_bitmap >= 0) {
> 		bitmap_parallel.buf = malloc(BUFSIZE_BITMAP);
> 		if (bitmap_parallel.buf == NULL){
> 			ERRMSG("Can't allocate memory for bitmap_parallel.buf. %s\n",
>@@ -7628,7 +7628,7 @@ kdump_thread_function_cyclic(void *arg) {
> 			pthread_mutex_lock(&info->current_pfn_mutex);
> 			for (pfn = info->current_pfn; pfn < cycle->end_pfn; pfn++) {
> 				dumpable = is_dumpable(
>-					info->fd_bitmap ? &bitmap_parallel : info->bitmap2,
>+					info->fd_bitmap >= 0 ? &bitmap_parallel : info->bitmap2,
> 					pfn,
> 					cycle);
> 				if (dumpable)
>@@ -7723,7 +7723,7 @@ next:
> 	retval = NULL;
>
> fail:
>-	if (bitmap_memory_parallel.fd > 0)
>+	if (bitmap_memory_parallel.fd >= 0)
> 		close(bitmap_memory_parallel.fd);
> 	if (bitmap_parallel.buf != NULL)
> 		free(bitmap_parallel.buf);
>@@ -8461,7 +8461,7 @@ out:
>
> int
> write_kdump_bitmap1(struct cycle *cycle) {
>-	if (info->bitmap1->fd) {
>+	if (info->bitmap1->fd >= 0) {
> 		return write_kdump_bitmap1_file();
> 	} else {
> 		return write_kdump_bitmap1_buffer(cycle);
>@@ -8470,7 +8470,7 @@ write_kdump_bitmap1(struct cycle *cycle) {
>
> int
> write_kdump_bitmap2(struct cycle *cycle) {
>-	if (info->bitmap2->fd) {
>+	if (info->bitmap2->fd >= 0) {
> 		return write_kdump_bitmap2_file();
> 	} else {
> 		return write_kdump_bitmap2_buffer(cycle);
>@@ -8597,9 +8597,10 @@ close_vmcoreinfo(void)
> void
> close_dump_memory(void)
> {
>-	if ((info->fd_memory = close(info->fd_memory)) < 0)
>+	if (close(info->fd_memory) < 0)
> 		ERRMSG("Can't close the dump memory(%s). %s\n",
> 		    info->name_memory, strerror(errno));
>+	info->fd_memory = -1;
> }
>
> void
>@@ -8608,9 +8609,10 @@ close_dump_file(void)
> 	if (info->flag_flatten)
> 		return;
>
>-	if ((info->fd_dumpfile = close(info->fd_dumpfile)) < 0)
>+	if (close(info->fd_dumpfile) < 0)
> 		ERRMSG("Can't close the dump file(%s). %s\n",
> 		    info->name_dumpfile, strerror(errno));
>+	info->fd_dumpfile = -1;
> }
>
> void
>@@ -8620,9 +8622,10 @@ close_dump_bitmap(void)
> 	    && !info->flag_sadump && !info->flag_mem_usage)
> 		return;
>
>-	if ((info->fd_bitmap = close(info->fd_bitmap)) < 0)
>+	if (close(info->fd_bitmap) < 0)
> 		ERRMSG("Can't close the bitmap file(%s). %s\n",
> 		    info->name_bitmap, strerror(errno));
>+	info->fd_bitmap = -1;
> 	free(info->name_bitmap);
> 	info->name_bitmap = NULL;
> }
>@@ -8631,16 +8634,18 @@ void
> close_kernel_file(void)
> {
> 	if (info->name_vmlinux) {
>-		if ((info->fd_vmlinux = close(info->fd_vmlinux)) < 0) {
>+		if (close(info->fd_vmlinux) < 0) {
> 			ERRMSG("Can't close the kernel file(%s). %s\n",
> 			    info->name_vmlinux, strerror(errno));
> 		}
>+		info->fd_vmlinux = -1;
> 	}
> 	if (info->name_xen_syms) {
>-		if ((info->fd_xen_syms = close(info->fd_xen_syms)) < 0) {
>+		if (close(info->fd_xen_syms) < 0) {
> 			ERRMSG("Can't close the kernel file(%s). %s\n",
> 			    info->name_xen_syms, strerror(errno));
> 		}
>+		info->fd_xen_syms = -1;
> 	}
> }
>
>@@ -10202,7 +10207,7 @@ reassemble_kdump_header(void)
>
> 	ret = TRUE;
> out:
>-	if (fd > 0)
>+	if (fd >= 0)
> 		close(fd);
> 	free(buf_bitmap);
>
>@@ -10212,7 +10217,7 @@ out:
> int
> reassemble_kdump_pages(void)
> {
>-	int i, fd = 0, ret = FALSE;
>+	int i, fd = -1, ret = FALSE;
> 	off_t offset_first_ph, offset_ph_org, offset_eraseinfo;
> 	off_t offset_data_new, offset_zero_page = 0;
> 	mdf_pfn_t pfn, start_pfn, end_pfn;
>@@ -10336,7 +10341,7 @@ reassemble_kdump_pages(void)
> 			offset_data_new += pd.size;
> 		}
> 		close(fd);
>-		fd = 0;
>+		fd = -1;
> 	}
> 	if (!write_cache_bufsz(&cd_pd))
> 		goto out;
>@@ -10379,7 +10384,7 @@ reassemble_kdump_pages(void)
> 		size_eraseinfo += SPLITTING_SIZE_EI(i);
>
> 		close(fd);
>-		fd = 0;
>+		fd = -1;
> 	}
> 	if (size_eraseinfo) {
> 		if (!write_cache_bufsz(&cd_data))
>@@ -10400,7 +10405,7 @@ out:
>
> 	if (data)
> 		free(data);
>-	if (fd > 0)
>+	if (fd >= 0)
> 		close(fd);
>
> 	return ret;
>@@ -10973,6 +10978,11 @@ main(int argc, char *argv[])
> 		    strerror(errno));
> 		goto out;
> 	}
>+	info->fd_vmlinux = -1;
>+	info->fd_xen_syms = -1;
>+	info->fd_memory = -1;
>+	info->fd_dumpfile = -1;
>+	info->fd_bitmap = -1;
> 	initialize_tables();
>
> 	/*
>@@ -11268,11 +11278,11 @@ out:
> 				free(info->bitmap_memory->buf);
> 			free(info->bitmap_memory);
> 		}
>-		if (info->fd_memory)
>+		if (info->fd_memory >= 0)
> 			close(info->fd_memory);
>-		if (info->fd_dumpfile)
>+		if (info->fd_dumpfile >= 0)
> 			close(info->fd_dumpfile);
>-		if (info->fd_bitmap)
>+		if (info->fd_bitmap >= 0)
> 			close(info->fd_bitmap);
> 		if (vt.node_online_map != NULL)
> 			free(vt.node_online_map);
>diff --git a/makedumpfile.h b/makedumpfile.h
>index 533e5b8..1814139 100644
>--- a/makedumpfile.h
>+++ b/makedumpfile.h
>@@ -1955,7 +1955,7 @@ is_dumpable_file(struct dump_bitmap *bitmap, mdf_pfn_t pfn)
> static inline int
> is_dumpable(struct dump_bitmap *bitmap, mdf_pfn_t pfn, struct cycle *cycle)
> {
>-	if (bitmap->fd == 0) {
>+	if (bitmap->fd < 0) {
> 		return is_dumpable_buffer(bitmap, pfn, cycle);
> 	} else {
> 		return is_dumpable_file(bitmap, pfn);
>diff --git a/sadump_info.c b/sadump_info.c
>index 5ff5595..f77a020 100644
>--- a/sadump_info.c
>+++ b/sadump_info.c
>@@ -1853,6 +1853,7 @@ sadump_add_diskset_info(char *name_memory)
> 	}
>
> 	si->diskset_info[si->num_disks - 1].name_memory = name_memory;
>+	si->diskset_info[si->num_disks - 1].fd_memory = -1;
>
> 	return TRUE;
> }
>@@ -1917,7 +1918,7 @@ free_sadump_info(void)
> 		int i;
>
> 		for (i = 1; i < si->num_disks; ++i) {
>-			if (si->diskset_info[i].fd_memory)
>+			if (si->diskset_info[i].fd_memory >= 0)
> 				close(si->diskset_info[i].fd_memory);
> 			if (si->diskset_info[i].sph_memory)
> 				free(si->diskset_info[i].sph_memory);
>--
>2.6.6


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