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10:17:40 +0000 Message-ID: <4a9259a9675e48e083139c22f7a86c8c@xiaomi.com> References: <20230719065459.60083-1-hsiangkao@linux.alibaba.com> In-Reply-To: <20230719065459.60083-1-hsiangkao@linux.alibaba.com> Accept-Language: zh-CN, en-US Content-Language: zh-CN X-MS-Has-Attach: X-MS-TNEF-Correlator: x-originating-ip: [10.237.8.11] Content-Type: multipart/alternative; boundary="_000_4a9259a9675e48e083139c22f7a86c8cxiaomicom_" MIME-Version: 1.0 X-BeenThere: linux-erofs@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Development of Linux EROFS file system List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: =?utf-8?b?5a2Z5aOr5p2wIHZpYSBMaW51eC1lcm9mcw==?= Reply-To: =?gb2312?B?y+/Kv73c?= Cc: LKML Errors-To: linux-erofs-bounces+linux-erofs=archiver.kernel.org@lists.ozlabs.org Sender: "Linux-erofs" --_000_4a9259a9675e48e083139c22f7a86c8cxiaomicom_ Content-Type: text/plain; charset="gb2312" Content-Transfer-Encoding: base64 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When handling dedup= licated compressed data, there can be multiple
decompressed extents p= ointing to the same compressed data in one shot.

In such cases, the bve= cs which belong to the longest extent will be
selected as the primar= y bvecs for real decompressors to decode and the
other duplicated bvecs= will be directly copied from the primary bvecs.

Previously, only relat= ive offsets of the longest extent was checked to
decompress the primary= bvecs.  On rare occasions, it can be incorrect
if there are several e= xtents with the same start relative offset.
As a result, some shor= t bvecs could be selected for decompression and
then cause data corrup= tion.

For example, as Shijie= Sun reported off-list, considering the following
extents of a file:
 117:  = 903345..  915250 |   11905 :     385024= ..    389120 |    4096
...
 119:  = 919729..  930323 |   10594 :     385024= ..    389120 |    4096
...
 124:  = 968881..  980786 |   11905 :     385024= ..    389120 |    4096

The start relative off= set is the same: 2225, but extent 119 (919729..
930323) is shorter tha= n the others.

Let's restrict the bve= c length in addition to the start offset if bvecs
are not full.
Reported-by: Shijie Su= n <sunshijie@xiaomi.com>
Fixes: 5c2a64252c5d (&= quot;erofs: introduce partial-referenced pclusters")
Signed-off-by: Gao Xia= ng <hsiangkao@linux.alibaba.com>
---
 fs/erofs/zdata.c= | 7 ++++---
 1 file changed, = 4 insertions(+), 3 deletions(-)

diff --git a/fs/erofs/= zdata.c b/fs/erofs/zdata.c
index b69d89a11dd0..de= 4f12152b62 100644
--- a/fs/erofs/zdata.c=
+++ b/fs/e= rofs/zdata.c
@@ -1144,10 +1144,= 11 @@ static void z_erofs_do_decompressed_bvec(struct z_erofs_decompress_ba= ckend *be,
   &nbs= p;            &= nbsp;           &nbs= p;            struct= z_erofs_bvec *bvec)
 {
   &nbs= p;    struct z_erofs_bvec_item *item;
+   = ;    unsigned int pgnr;

-   &nb= sp;   if (!((bvec->offset + be->pcl->pageofs_out) &a= mp; ~PAGE_MASK)) {
-   &nb= sp;           unsigned in= t pgnr;
-
+   = ;    if (!((bvec->offset + be->pcl->pageofs_out= ) & ~PAGE_MASK) &&
+   = ;        (bvec->end =3D=3D PAGE_SIZE = ||
+   = ;         bvec->offset + bve= c->end =3D=3D be->pcl->length)) {
   &nbs= p;            pgnr = =3D (bvec->offset + be->pcl->pageofs_out) >> PAGE_SHIFT;=
   &nbs= p;            DBG_BU= GON(pgnr >=3D be->nr_pages);
   &nbs= p;            if (!b= e->decompressed_pages[pgnr]) {
--
2.24.4
Tested-by Shijie Sun <sunshijie@xiaomi.com>


Thanks, 

Sun Shijie

=B7=A2=BC=FE=C8=CB: Gao X= iang <hsiangkao@linux.alibaba.com>
=B7=A2=CB=CD=CA=B1=BC=E4: 2023=C4=EA7=D4=C219=C8=D5 14:54:59
=CA=D5=BC=FE=C8=CB: linux-erofs@lists.ozlabs.org
=B3=AD=CB=CD: LKML; Gao Xiang; =CB=EF=CA=BF=BD=DC
=D6=F7=CC=E2: [External Mail][PATCH] erofs: fix wrong primary bvec s= election on deduplicated extents
 
[=CD=E2=B2=BF=D3=CA=BC=FE] =B4=CB=D3=CA=BC=FE=C0= =B4=D4=B4=D3=DA=D0=A1=C3=D7=B9=AB=CB=BE=CD=E2=B2=BF=A3=AC=C7=EB=BD=F7=C9=F7= =B4=A6=C0=ED=A1=A3=C8=F4=B6=D4=D3=CA=BC=FE=B0=B2=C8=AB=D0=D4=B4=E6=D2=C9=A3= =AC=C7=EB=BD=AB=D3=CA=BC=FE=D7=AA=B7=A2=B8=F8misec@xiaomi.com=BD=F8=D0=D0= =B7=B4=C0=A1

When handling deduplicated compressed data, there can be multiple
decompressed extents pointing to the same compressed data in one shot.

In such cases, the bvecs which belong to the longest extent will be
selected as the primary bvecs for real decompressors to decode and the
other duplicated bvecs will be directly copied from the primary bvecs.

Previously, only relative offsets of the longest extent was checked to
decompress the primary bvecs.  On rare occasions, it can be incorrect<= br> if there are several extents with the same start relative offset.
As a result, some short bvecs could be selected for decompression and
then cause data corruption.

For example, as Shijie Sun reported off-list, considering the following
extents of a file:
 117:   903345..  915250 |   11905 : &nb= sp;   385024..    389120 |    4096<= br> ...
 119:   919729..  930323 |   10594 : &nb= sp;   385024..    389120 |    4096<= br> ...
 124:   968881..  980786 |   11905 : &nb= sp;   385024..    389120 |    4096<= br>
The start relative offset is the same: 2225, but extent 119 (919729..
930323) is shorter than the others.

Let's restrict the bvec length in addition to the start offset if bvecs
are not full.

Reported-by: Shijie Sun <sunshijie@xiaomi.com>
Fixes: 5c2a64252c5d ("erofs: introduce partial-referenced pclusters&qu= ot;)
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>
---
 fs/erofs/zdata.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/erofs/zdata.c b/fs/erofs/zdata.c
index b69d89a11dd0..de4f12152b62 100644
--- a/fs/erofs/zdata.c
+++ b/fs/erofs/zdata.c
@@ -1144,10 +1144,11 @@ static void z_erofs_do_decompressed_bvec(struct= z_erofs_decompress_backend *be,
            &nb= sp;            =             &nb= sp;   struct z_erofs_bvec *bvec)
 {
        struct z_erofs_bvec_item *item;<= br> +       unsigned int pgnr;

-       if (!((bvec->offset + be->p= cl->pageofs_out) & ~PAGE_MASK)) {
-            &n= bsp;  unsigned int pgnr;
-
+       if (!((bvec->offset + be-&= gt;pcl->pageofs_out) & ~PAGE_MASK) &&
+           (bvec->= ;end =3D=3D PAGE_SIZE ||
+            bve= c->offset + bvec->end =3D=3D be->pcl->length)) {
            &nb= sp;   pgnr =3D (bvec->offset + be->pcl->pageofs_out)= >> PAGE_SHIFT;
            &nb= sp;   DBG_BUGON(pgnr >=3D be->nr_pages);
            &nb= sp;   if (!be->decompressed_pages[pgnr]) {
--
2.24.4

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