[PATCH AUTOSEL 4.19 2/3] scsi: qedi: Fix crash while reading debugfs attribute

[Sasha Levin <sashal@kernel.org>]

From: Manish Rangankar <mrangankar@marvell.com>

[ Upstream commit 28027ec8e32ecbadcd67623edb290dad61e735b5 ]

The qedi_dbg_do_not_recover_cmd_read() function invokes sprintf() directly
on a __user pointer, which results into the crash.

To fix this issue, use a small local stack buffer for sprintf() and then
call simple_read_from_buffer(), which in turns make the copy_to_user()
call.

BUG: unable to handle page fault for address: 00007f4801111000
PGD 8000000864df6067 P4D 8000000864df6067 PUD 864df7067 PMD 846028067 PTE 0
Oops: 0002 [#1] PREEMPT SMP PTI
Hardware name: HPE ProLiant DL380 Gen10/ProLiant DL380 Gen10, BIOS U30 06/15/2023
RIP: 0010:memcpy_orig+0xcd/0x130
RSP: 0018:ffffb7a18c3ffc40 EFLAGS: 00010202
RAX: 00007f4801111000 RBX: 00007f4801111000 RCX: 000000000000000f
RDX: 000000000000000f RSI: ffffffffc0bfd7a0 RDI: 00007f4801111000
RBP: ffffffffc0bfd7a0 R08: 725f746f6e5f6f64 R09: 3d7265766f636572
R10: ffffb7a18c3ffd08 R11: 0000000000000000 R12: 00007f4881110fff
R13: 000000007fffffff R14: ffffb7a18c3ffca0 R15: ffffffffc0bfd7af
FS:  00007f480118a740(0000) GS:ffff98e38af00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f4801111000 CR3: 0000000864b8e001 CR4: 00000000007706e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
PKRU: 55555554
Call Trace:
 <TASK>
 ? __die_body+0x1a/0x60
 ? page_fault_oops+0x183/0x510
 ? exc_page_fault+0x69/0x150
 ? asm_exc_page_fault+0x22/0x30
 ? memcpy_orig+0xcd/0x130
 vsnprintf+0x102/0x4c0
 sprintf+0x51/0x80
 qedi_dbg_do_not_recover_cmd_read+0x2f/0x50 [qedi 6bcfdeeecdea037da47069eca2ba717c84a77324]
 full_proxy_read+0x50/0x80
 vfs_read+0xa5/0x2e0
 ? folio_add_new_anon_rmap+0x44/0xa0
 ? set_pte_at+0x15/0x30
 ? do_pte_missing+0x426/0x7f0
 ksys_read+0xa5/0xe0
 do_syscall_64+0x58/0x80
 ? __count_memcg_events+0x46/0x90
 ? count_memcg_event_mm+0x3d/0x60
 ? handle_mm_fault+0x196/0x2f0
 ? do_user_addr_fault+0x267/0x890
 ? exc_page_fault+0x69/0x150
 entry_SYSCALL_64_after_hwframe+0x72/0xdc
RIP: 0033:0x7f4800f20b4d

Tested-by: Martin Hoyer <mhoyer@redhat.com>
Reviewed-by: John Meneghini <jmeneghi@redhat.com>
Signed-off-by: Manish Rangankar <mrangankar@marvell.com>
Link: https://lore.kernel.org/r/20240415072155.30840-1-mrangankar@marvell.com
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/scsi/qedi/qedi_debugfs.c | 12 ++++--------
 1 file changed, 4 insertions(+), 8 deletions(-)

diff --git a/drivers/scsi/qedi/qedi_debugfs.c b/drivers/scsi/qedi/qedi_debugfs.c
index fd914ca4149a8..6bb5f2b31b881 100644
--- a/drivers/scsi/qedi/qedi_debugfs.c
+++ b/drivers/scsi/qedi/qedi_debugfs.c
@@ -136,15 +136,11 @@ static ssize_t
 qedi_dbg_do_not_recover_cmd_read(struct file *filp, char __user *buffer,
 				 size_t count, loff_t *ppos)
 {
-	size_t cnt = 0;
-
-	if (*ppos)
-		return 0;
+	char buf[64];
+	int len;
 
-	cnt = sprintf(buffer, "do_not_recover=%d\n", qedi_do_not_recover);
-	cnt = min_t(int, count, cnt - *ppos);
-	*ppos += cnt;
-	return cnt;
+	len = sprintf(buf, "do_not_recover=%d\n", qedi_do_not_recover);
+	return simple_read_from_buffer(buffer, count, ppos, buf, len);
 }
 
 static int
-- 
2.43.0