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Date: Sat, 5 May 2007 19:02:44 +0530
From: "Satyam Sharma" <satyam.sharma@...il.com>
To: dedekind@...radead.org
Cc: "Florin Malita" <fmalita@...il.com>,
"Andrew Morton" <akpm@...ux-foundation.org>,
linux-mtd@...ts.infradead.org,
"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] UBI: dereference after kfree in create_vtbl
On 5/5/07, Artem Bityutskiy <dedekind@...radead.org> wrote:
> [...]
> I've put the fix here:
> http://git.infradead.org/?p=users/dedekind/ubi-2.6.git;a=commit;h=5125237efb6a3309fbf5b9a7a21aaf716787f2a2
> write_error:
> if (err == -EIO && ++tries <= 5) {
> /*
> * Probably this physical eraseblock went bad, try to pick
> * another one.
> */
> list_add_tail(&new_seb->u.list, &si->corr);
> goto retry;
> }
> kfree(new_seb);
> out_free:
> ubi_free_vid_hdr(ubi, vid_hdr);
> return err;
Ummm ...
1. "if (err == -EIO)" applies to adding new_seb to the corrupted list,
and not to retrying. We wouldn't want _not_ to retry if there's some
other error, or would we?
2. "if (++tries <= 5)" applies to "goto retry" and not to adding
new_seb to the corrupted list. If we hit write failure for the 5th
time and err == -EIO, we should still be adding it to corrupted list,
but not retry, of course. Otherwise we would add the first 4 write
failure (with -EIO) eraseblocks to si->corr, but the 5th _similar_
case is ... just freed?
So:
write_error:
/*
* Probably this physical eraseblock went bad, add it to the
* corrupted list. Else, just release it.
*/
if (err == -EIO)
/* list_add_tail(&new_seb->u.list, &si->corr); */
__ubi_scan_add_to_list(si, new_seb, &si->corr);
else
kfree(new_seb);
/* Try to pick another one */
if (++tries <= 5)
goto retry;
out_free:
ubi_free_vid_hdr(ubi, vid_hdr);
return err;
And in case you want to avoid the list_add_tail there, the following
(I'm fine with whichever way, of course):
diff -ruNp a/drivers/mtd/ubi/scan.c b/drivers/mtd/ubi/scan.c
--- a/drivers/mtd/ubi/scan.c 2007-05-05 10:52:47.000000000 +0530
+++ b/drivers/mtd/ubi/scan.c 2007-05-05 11:47:26.000000000 +0530
@@ -55,29 +55,37 @@ static int paranoid_check_si(const struc
static struct ubi_ec_hdr *ech;
static struct ubi_vid_hdr *vidh;
-int ubi_scan_add_to_list(struct ubi_scan_info *si, int pnum, int ec,
- struct list_head *list)
+void __ubi_scan_add_to_list(struct ubi_scan_info *si,
+ struct ubi_scan_leb *seb,
+ struct list_head *list)
{
- struct ubi_scan_leb *seb;
-
if (list == &si->free)
- dbg_bld("add to free: PEB %d, EC %d", pnum, ec);
+ dbg_bld("add to free: PEB %d, EC %d", seb->pnum, seb->ec);
else if (list == &si->erase)
- dbg_bld("add to erase: PEB %d, EC %d", pnum, ec);
+ dbg_bld("add to erase: PEB %d, EC %d", seb->pnum, seb->ec);
else if (list == &si->corr)
- dbg_bld("add to corrupted: PEB %d, EC %d", pnum, ec);
+ dbg_bld("add to corrupted: PEB %d, EC %d", seb->pnum, seb->ec);
else if (list == &si->alien)
- dbg_bld("add to alien: PEB %d, EC %d", pnum, ec);
+ dbg_bld("add to alien: PEB %d, EC %d", seb->pnum, seb->ec);
else
BUG();
+ list_add_tail(&seb->u.list, list);
+}
+
+int ubi_scan_add_to_list(struct ubi_scan_info *si, int pnum, int ec,
+ struct list_head *list)
+{
+ struct ubi_scan_leb *seb;
+
seb = kmalloc(sizeof(struct ubi_scan_leb), GFP_KERNEL);
if (unlikely(!seb))
return -ENOMEM;
seb->pnum = pnum;
seb->ec = ec;
- list_add_tail(&seb->u.list, list);
+ __ubi_scan_add_to_list(si, seb, list);
+
return 0;
}
diff -ruNp a/drivers/mtd/ubi/scan.h b/drivers/mtd/ubi/scan.h
--- a/drivers/mtd/ubi/scan.h 2007-05-05 10:55:24.000000000 +0530
+++ b/drivers/mtd/ubi/scan.h 2007-05-05 10:55:01.000000000 +0530
@@ -147,6 +147,9 @@ static inline void ubi_scan_move_to_list
list_add_tail(&seb->u.list, list);
}
+void __ubi_scan_add_to_list(struct ubi_scan_info *si,
+ struct ubi_scan_leb *seb,
+ struct list_head *list);
int ubi_scan_add_to_list(struct ubi_scan_info *si, int pnum, int ec,
struct list_head *list);
int ubi_scan_add_used(const struct ubi_device *ubi, struct ubi_scan_info *si,
-
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