[PATCH] makedumpfile: bugfix: fix a div-by-zero problem

[PATCH] makedumpfile: bugfix: fix a div-by-zero problem

[Wang Nan]

In makedumpfile.c, we want the progress printed 10000 times.
It is tested by:

(num_dumped % per) == 0

where per is num_dumpable / 10000.

However, if num_dumpable less than 10000, num_dumped % per causes a
divide-by-zero problem, triggers a SIGFPE.

This patch makes sure per never be 0.

Signed-off-by: Wang Nan <wangnan0@huawei.com>
Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
Cc: kexec@lists.infradead.org
Cc: Geng Hui <hui.geng@huawei.com>
Cc: Simon Horman <horms@verge.net.au>
---
 makedumpfile.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/makedumpfile.c b/makedumpfile.c
index 23251a1..d71977a 100644
--- a/makedumpfile.c
+++ b/makedumpfile.c
@@ -5621,6 +5621,7 @@ write_elf_pages(struct cache_data *cd_header, struct cache_data *cd_page)
 
 	num_dumpable = get_num_dumpable();
 	per = num_dumpable / 10000;
+	per = per ? per : 1;
 
 	off_seg_load    = info->offset_load_dumpfile;
 	cd_page->offset = info->offset_load_dumpfile;
@@ -5906,6 +5907,7 @@ write_elf_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_page)
 
 	num_dumpable = info->num_dumpable;
 	per = num_dumpable / 10000;
+	per = per ? per : 1;
 
 	off_seg_load   = info->offset_load_dumpfile;
 	cd_page->offset = info->offset_load_dumpfile;
@@ -6164,6 +6166,7 @@ write_kdump_pages(struct cache_data *cd_header, struct cache_data *cd_page)
 
 	num_dumpable = get_num_dumpable();
 	per = num_dumpable / 10000;
+	per = per ? per : 1;
 
 	/*
 	 * Calculate the offset of the page data.
@@ -6365,6 +6368,7 @@ write_kdump_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_pag
 	}
 
 	per = info->num_dumpable / 10000;
+	per = per ? per : 1;
 
 	/*
 	 * Set a fileoffset of Physical Address 0x0.
-- 
1.8.4


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RE: [PATCH] makedumpfile: bugfix: fix a div-by-zero problem

[Atsushi Kumagai]

>In makedumpfile.c, we want the progress printed 10000 times.
>It is tested by:
>
>(num_dumped % per) == 0
>
>where per is num_dumpable / 10000.
>
>However, if num_dumpable less than 10000, num_dumped % per causes a
>divide-by-zero problem, triggers a SIGFPE.
>
>This patch makes sure per never be 0.

Good fix, thanks.

Acked-by: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>

>Signed-off-by: Wang Nan <wangnan0@huawei.com>
>Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
>Cc: kexec@lists.infradead.org
>Cc: Geng Hui <hui.geng@huawei.com>
>Cc: Simon Horman <horms@verge.net.au>
>---
> makedumpfile.c | 4 ++++
> 1 file changed, 4 insertions(+)
>
>diff --git a/makedumpfile.c b/makedumpfile.c
>index 23251a1..d71977a 100644
>--- a/makedumpfile.c
>+++ b/makedumpfile.c
>@@ -5621,6 +5621,7 @@ write_elf_pages(struct cache_data *cd_header, struct cache_data *cd_page)
>
> 	num_dumpable = get_num_dumpable();
> 	per = num_dumpable / 10000;
>+	per = per ? per : 1;
>
> 	off_seg_load    = info->offset_load_dumpfile;
> 	cd_page->offset = info->offset_load_dumpfile;
>@@ -5906,6 +5907,7 @@ write_elf_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_page)
>
> 	num_dumpable = info->num_dumpable;
> 	per = num_dumpable / 10000;
>+	per = per ? per : 1;
>
> 	off_seg_load   = info->offset_load_dumpfile;
> 	cd_page->offset = info->offset_load_dumpfile;
>@@ -6164,6 +6166,7 @@ write_kdump_pages(struct cache_data *cd_header, struct cache_data *cd_page)
>
> 	num_dumpable = get_num_dumpable();
> 	per = num_dumpable / 10000;
>+	per = per ? per : 1;
>
> 	/*
> 	 * Calculate the offset of the page data.
>@@ -6365,6 +6368,7 @@ write_kdump_pages_cyclic(struct cache_data *cd_header, struct cache_data *cd_pag
> 	}
>
> 	per = info->num_dumpable / 10000;
>+	per = per ? per : 1;
>
> 	/*
> 	 * Set a fileoffset of Physical Address 0x0.
>--
>1.8.4

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