[PATCH] Fix NULL ->nsproxy dereference in /proc/*/mounts
/proc/*/mounstats was fixed, all right, but... To reproduce: while true; do find /proc -type f 2>/dev/null | xargs cat 1>/dev/null 2>/dev/null; done BUG: unable to handle kernel NULL pointer dereference at virtual address 0000000c printing eip: c01754df *pde = 00000000 Oops: 0000 [#28] Modules linked in: af_packet ohci_hcd e1000 ehci_hcd uhci_hcd usbcore xfs CPU: 0 EIP: 0060:[<c01754df>] Not tainted VLI EFLAGS: 00010286 (2.6.20-rc5 #1) EIP is at mounts_open+0x1c/0xac eax: 00000000 ebx: d5898ac0 ecx: d1d27b18 edx: d1d27a50 esi: e6083e10 edi: d3c87f38 ebp: d5898ac0 esp: d3c87ef0 ds: 007b es: 007b ss: 0068 Process cat (pid: 18071, ti=d3c86000 task=f7d5f070 task.ti=d3c86000) Stack: d5898ac0 e6083e10 d3c87f38 c01754c3 c0147c91 c18c52c0 d343f314 d5898ac0 00008000 d3c87f38 ffffff9c c0147e09 d5898ac0 00000000 00000000 c0147e4b 00000000 d3c87f38 d343f314 c18c52c0 c015e53e 00001000 08051000 00000101 Call Trace: [<c01754c3>] mounts_open+0x0/0xac [<c0147c91>] __dentry_open+0xa1/0x18c [<c0147e09>] nameidata_to_filp+0x31/0x3a [<c0147e4b>] do_filp_open+0x39/0x40 [<c015e53e>] seq_read+0x128/0x2aa [<c0147e8c>] do_sys_open+0x3a/0x6d [<c0147efa>] sys_open+0x1c/0x20 [<c0102b76>] sysenter_past_esp+0x5f/0x85 [<c02a0033>] unix_stream_recvmsg+0x3bf/0x4bf ======================= Code: 5d c3 89 d8 e8 06 e0 f9 ff eb bd 0f 0b eb fe 55 57 56 53 89 d5 8b 40 f0 31 d2 e8 02 c1 fa ff 89 c2 85 c0 74 5c 8b 80 48 04 00 00 <8b> 58 0c 85 db 74 02 ff 03 ff 4a 08 0f 94 c0 84 c0 75 74 85 db EIP: [<c01754df>] mounts_open+0x1c/0xac SS:ESP 0068:d3c87ef0 Signed-off-by: Alexey Dobriyan <adobriyan@openvz.org> --- fs/proc/base.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) --- a/fs/proc/base.c +++ b/fs/proc/base.c @@ -371,9 +371,11 @@ static int mounts_open(struct inode *ino if (task) { task_lock(task); - ns = task->nsproxy->mnt_ns; - if (ns) - get_mnt_ns(ns); + if (task->nsproxy) { + ns = task->nsproxy->mnt_ns; + if (ns) + get_mnt_ns(ns); + } task_unlock(task); put_task_struct(task); }
Re: [PATCH] Fix NULL ->nsproxy dereference in /proc/*/mounts
Quoting Alexey Dobriyan (adobriyan@openvz.org): > /proc/*/mounstats was fixed, all right, but... > > To reproduce: > > while true; do > find /proc -type f 2>/dev/null | xargs cat 1>/dev/null 2>/dev/null; > done > > BUG: unable to handle kernel NULL pointer dereference at virtual address 0000000c > printing eip: > c01754df > *pde = 00000000 > Oops: 0000 [#28] > Modules linked in: af_packet ohci_hcd e1000 ehci_hcd uhci_hcd usbcore xfs > CPU: 0 > EIP: 0060:[<c01754df>] Not tainted VLI > EFLAGS: 00010286 (2.6.20-rc5 #1) > EIP is at mounts_open+0x1c/0xac > eax: 00000000 ebx: d5898ac0 ecx: d1d27b18 edx: d1d27a50 > esi: e6083e10 edi: d3c87f38 ebp: d5898ac0 esp: d3c87ef0 > ds: 007b es: 007b ss: 0068 > Process cat (pid: 18071, ti=d3c86000 task=f7d5f070 task.ti=d3c86000) > Stack: d5898ac0 e6083e10 d3c87f38 c01754c3 c0147c91 c18c52c0 d343f314 d5898ac0 > 00008000 d3c87f38 ffffff9c c0147e09 d5898ac0 00000000 00000000 c0147e4b > 00000000 d3c87f38 d343f314 c18c52c0 c015e53e 00001000 08051000 00000101 > Call Trace: > [<c01754c3>] mounts_open+0x0/0xac > [<c0147c91>] __dentry_open+0xa1/0x18c > [<c0147e09>] nameidata_to_filp+0x31/0x3a > [<c0147e4b>] do_filp_open+0x39/0x40 > [<c015e53e>] seq_read+0x128/0x2aa > [<c0147e8c>] do_sys_open+0x3a/0x6d > [<c0147efa>] sys_open+0x1c/0x20 > [<c0102b76>] sysenter_past_esp+0x5f/0x85 > [<c02a0033>] unix_stream_recvmsg+0x3bf/0x4bf > ======================= > Code: 5d c3 89 d8 e8 06 e0 f9 ff eb bd 0f 0b eb fe 55 57 56 53 89 d5 8b 40 f0 31 d2 e8 02 c1 fa ff 89 c2 85 c0 74 5c 8b 80 48 04 00 00 <8b> 58 0c 85 db 74 02 ff 03 ff 4a 08 0f 94 c0 84 c0 75 74 85 db > EIP: [<c01754df>] mounts_open+0x1c/0xac SS:ESP 0068:d3c87ef0 > > Signed-off-by: Alexey Dobriyan <adobriyan@openvz.org> Yup, race with do_exit()'s call to exit_namespaces(). Thanks for the patch. Acked-by: Serge Hallyn <serue@us.ibm.com> > --- > > fs/proc/base.c | 8 +++++--- > 1 file changed, 5 insertions(+), 3 deletions(-) > > --- a/fs/proc/base.c > +++ b/fs/proc/base.c > @@ -371,9 +371,11 @@ static int mounts_open(struct inode *ino > > if (task) { > task_lock(task); > - ns = task->nsproxy->mnt_ns; > - if (ns) > - get_mnt_ns(ns); > + if (task->nsproxy) { > + ns = task->nsproxy->mnt_ns; > + if (ns) > + get_mnt_ns(ns); > + } > task_unlock(task); > put_task_struct(task); > } > > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/