CVE-2024-49884

================================================================== BUG: KASAN: slab-use-after-free in ext4splitextentat+0xba8/0xcc0 Read of size 2 at addr ffff88810548ed08 by task kworker/u20:0/40 CPU: 0 PID: 40 Comm: kworker/u20:0 Not tainted 6.9.0-dirty #724 Call Trace: <TASK> kasanreport+0x93/0xc0 ext4splitextentat+0xba8/0xcc0 ext4splitextent.isra.0+0x18f/0x500 ext4splitconvertextents+0x275/0x750 ext4exthandleunwrittenextents+0x73e/0x1580 ext4extmapblocks+0xe20/0x2dc0 ext4mapblocks+0x724/0x1700 ext4do_writepages+0x12d6/0x2a70 [...]

Allocated by task 40: _kmallocnoprof+0x1ac/0x480 ext4findextent+0xf3b/0x1e70 ext4extmapblocks+0x188/0x2dc0 ext4mapblocks+0x724/0x1700 ext4do_writepages+0x12d6/0x2a70 [...]

Freed by task 40: kfree+0xf1/0x2b0 ext4findextent+0xa71/0x1e70 ext4extinsertextent+0xa22/0x3260 ext4splitextentat+0x3ef/0xcc0 ext4splitextent.isra.0+0x18f/0x500 ext4splitconvertextents+0x275/0x750 ext4exthandleunwrittenextents+0x73e/0x1580 ext4extmapblocks+0xe20/0x2dc0 ext4mapblocks+0x724/0x1700 ext4dowritepages+0x12d6/0x2a70

[...]

The flow of issue triggering is as follows:

ext4splitextentat path = *ppath ext4extinsertextent(ppath) ext4extcreatenewleaf(ppath) ext4findextent(origpath) path = *origpath readextenttreeblock // return -ENOMEM or -EIO ext4freeextpath(path) kfree(path) *origpath = NULL a. If err is -ENOMEM: ext4extdirty(path + path->pdepth) // path use-after-free !!! b. If err is -EIO and we have EXTDEBUG defined: ext4extshowleaf(path) eh = path[depth].p_hdr // path also use-after-free !!!

So when trying to zeroout or fix the extent length, call ext4findextent() to update the path.

In addition we use *ppath directly as an ext4extshowleaf() input to avoid possible use-after-free when EXTDEBUG is defined, and to avoid unnecessary path updates.

References

Affected packages

Debian:11 / linux

Package

Name: linux
Purl: pkg:deb/debian/linux?arch=source

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0Unknown introduced version / All previous versions are affected

Fixed

5.10.234-1

Affected versions

5.*

5.10.46-4

5.10.46-5

5.10.70-1~bpo10+1

5.10.70-1

5.10.84-1

5.10.92-1~bpo10+1

5.10.92-1

5.10.92-2

5.10.103-1~bpo10+1

5.10.103-1

5.10.106-1

5.10.113-1

5.10.120-1~bpo10+1

5.10.120-1

5.10.127-1

5.10.127-2~bpo10+1

5.10.127-2

5.10.136-1

5.10.140-1

5.10.148-1

5.10.149-1

5.10.149-2

5.10.158-1

5.10.158-2

5.10.162-1

5.10.178-1

5.10.178-2

5.10.178-3

5.10.179-1

5.10.179-2

5.10.179-3

5.10.179-4

5.10.179-5

5.10.191-1

5.10.197-1

5.10.205-1

5.10.205-2

5.10.209-1

5.10.209-2

5.10.216-1

5.10.218-1

5.10.221-1

5.10.223-1

5.10.226-1

Ecosystem specific

{
    "urgency": "not yet assigned"
}

Debian:12 / linux

Package

Name: linux
Purl: pkg:deb/debian/linux?arch=source

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0Unknown introduced version / All previous versions are affected

Fixed

6.1.115-1

Affected versions

6.*

6.1.27-1

6.1.37-1

6.1.38-1

6.1.38-2~bpo11+1

6.1.38-2

6.1.38-3

6.1.38-4~bpo11+1

6.1.38-4

6.1.52-1

6.1.55-1~bpo11+1

6.1.55-1

6.1.64-1

6.1.66-1

6.1.67-1

6.1.69-1~bpo11+1

6.1.69-1

6.1.76-1~bpo11+1

6.1.76-1

6.1.82-1

6.1.85-1

6.1.90-1~bpo11+1

6.1.90-1

6.1.94-1~bpo11+1

6.1.94-1

6.1.98-1

6.1.99-1

6.1.106-1

6.1.106-2

6.1.106-3

6.1.112-1

Ecosystem specific

{
    "urgency": "not yet assigned"
}

Debian:13 / linux

Package

Name: linux
Purl: pkg:deb/debian/linux?arch=source

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0Unknown introduced version / All previous versions are affected

Fixed

6.11.4-1

Ecosystem specific

{
    "urgency": "not yet assigned"
}

Debian:11 / linux-6.1

Package

Name: linux-6.1
Purl: pkg:deb/debian/linux-6.1?arch=source

Affected ranges

Type: ECOSYSTEM
Events: Introduced

0Unknown introduced version / All previous versions are affected

Fixed

6.1.119-1~deb11u1

Affected versions

6.*

6.1.106-3~deb11u1

6.1.106-3~deb11u2

6.1.106-3~deb11u3

6.1.112-1~deb11u1

Ecosystem specific

{
    "urgency": "not yet assigned"
}