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[brown paperbag] fix coredump breakage

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Let me count the ways in which I'd screwed up:

* when emitting a page, handling of gaps in coredump should happen
before fetching the current file position.
* fix for a problem that occurs on rather uncommon setups (and hadn't
been observed in the wild) had been sent very late in the cycle.
* ... with badly insufficient testing, introducing an easily
reproducible breakage.  Without giving it time to soak in -next.

Fucked-up-by: Al Viro <viro@zeniv.linux.org.uk>
Reported-by: "J. R. Okajima" <hooanon05g@gmail.com>
Tested-by: "J. R. Okajima" <hooanon05g@gmail.com>
Fixes: 06bbaa6dc53c "[coredump] don't use __kernel_write() on kmap_local_page()"
Cc: stable@kernel.org	# v6.0-only
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
This commit is contained in:
Al Viro 2022-10-03 20:26:08 -04:00
parent 4fe89d07dc
commit 4f526fef91
1 changed files with 2 additions and 1 deletions
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3
fs/coredump.c
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@ -841,7 +841,7 @@ static int dump_emit_page(struct coredump_params *cprm, struct page *page)
};
struct iov_iter iter;
struct file *file = cprm->file;
loff_t pos = file->f_pos;
loff_t pos;
ssize_t n;
if (cprm->to_skip) {
@ -853,6 +853,7 @@ static int dump_emit_page(struct coredump_params *cprm, struct page *page)
return 0;
if (dump_interrupted())
return 0;
pos = file->f_pos;
iov_iter_bvec(&iter, WRITE, &bvec, 1, PAGE_SIZE);
n = __kernel_write_iter(cprm->file, &iter, &pos);
if (n != PAGE_SIZE)