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authorSiddh Raman Pant <code@siddh.me>2022-08-23 19:08:10 +0300
committerJens Axboe <axboe@kernel.dk>2022-08-24 15:52:52 +0300
commitc490a0b5a4f36da3918181a8acdc6991d967c5f3 (patch)
tree56a3365ccda2e6cf444bb277ec27e7c83ffaed72 /drivers/block/loop.c
parent65fac0d54f374625b43a9d6ad1f2c212bd41f518 (diff)
downloadlinux-c490a0b5a4f36da3918181a8acdc6991d967c5f3.tar.xz
loop: Check for overflow while configuring loop
The userspace can configure a loop using an ioctl call, wherein a configuration of type loop_config is passed (see lo_ioctl()'s case on line 1550 of drivers/block/loop.c). This proceeds to call loop_configure() which in turn calls loop_set_status_from_info() (see line 1050 of loop.c), passing &config->info which is of type loop_info64*. This function then sets the appropriate values, like the offset. loop_device has lo_offset of type loff_t (see line 52 of loop.c), which is typdef-chained to long long, whereas loop_info64 has lo_offset of type __u64 (see line 56 of include/uapi/linux/loop.h). The function directly copies offset from info to the device as follows (See line 980 of loop.c): lo->lo_offset = info->lo_offset; This results in an overflow, which triggers a warning in iomap_iter() due to a call to iomap_iter_done() which has: WARN_ON_ONCE(iter->iomap.offset > iter->pos); Thus, check for negative value during loop_set_status_from_info(). Bug report: https://syzkaller.appspot.com/bug?id=c620fe14aac810396d3c3edc9ad73848bf69a29e Reported-and-tested-by: syzbot+a8e049cd3abd342936b6@syzkaller.appspotmail.com Cc: stable@vger.kernel.org Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org> Signed-off-by: Siddh Raman Pant <code@siddh.me> Reviewed-by: Christoph Hellwig <hch@lst.de> Link: https://lore.kernel.org/r/20220823160810.181275-1-code@siddh.me Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'drivers/block/loop.c')
-rw-r--r--drivers/block/loop.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index e3c0ba93c1a3..ad92192c7d61 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -979,6 +979,11 @@ loop_set_status_from_info(struct loop_device *lo,
lo->lo_offset = info->lo_offset;
lo->lo_sizelimit = info->lo_sizelimit;
+
+ /* loff_t vars have been assigned __u64 */
+ if (lo->lo_offset < 0 || lo->lo_sizelimit < 0)
+ return -EOVERFLOW;
+
memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE);
lo->lo_file_name[LO_NAME_SIZE-1] = 0;
lo->lo_flags = info->lo_flags;